Studio Technologies 545DC User manual

50727-0622, Issue 1
Copyright © 2022 by Studio Technologies, Inc., all rights reserved
studio-tech.com
User Guide
Issue 1, June 2022
This User Guide is applicable for serial numbers
M545DC-00151 and later with Application Firmware 1.00 and later
and STcontroller application version 3.08.00 and later.
Model 545DC
Intercom Interface

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Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 3
Model 545DC
INTERCOM INTERFACE
Table of Contents
Revision History ................................................................................................................................ 4
Introduction........................................................................................................................................ 5
Getting Started .................................................................................................................................. 8
Dante Configuration .......................................................................................................................... 12
Model 545DC Configuration.............................................................................................................. 14
Operation........................................................................................................................................... 16
Technical Notes................................................................................................................................. 21
Specifications .................................................................................................................................... 25
Appendix A–STcontroller Default Configuration Values..................................................................... 27
Appendix B– Graphical Description of the Installation Kit for Panel-Cutout or Surface-Mounting
Use (Order Code RMBK-10) ............................................................................................................. 28
Appendix C–Graphical Description of Left- or Right-Side Rack-Mount Installation Kit for
One “1/2- Rack” Unit (Order Code RMBK-11)................................................................................... 29
Appendix D–Graphical Description of Rack-Mount Installation Kit for Two “1/2- Rack” Units
(Order Code RMBK-12)..................................................................................................................... 30
Appendix E–Graphical Description of Center Rack-Mount Installation Kit for One “1/2- Rack”
Unit (Order Code RMBK-13) ............................................................................................................. 31

Issue 1, June 2022 Model 545DC User Guide
Page 4 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
Revision History
Issue 1, June 2022:
•Initial release.

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 5
Model 545DC
INTERCOM INTERFACE
Introduction
The Model 545DC Intercom Interface allows two
single-channel analog party-line (PL) intercom
circuits and associated user devices to be incorpo-
rated into Dante
®
audio-over-Ethernet applications.
Single-channel analog party-line (PL) intercom sys-
tems are commonly used in theater, entertainment,
and education applications where a simple, reliable,
low-cost, and easy-to-use solution is desired. Dante
has become a major method of interconnecting audio
signals and various devices using standard Ethernet
networks. The Model 545DC directly supports both
analog party-line (PL) and Dante, providing excel-
lent performance in both domains. Single-channel
analog party-line (PL) products from Clear-Com
®
are
directly compatible with the Model 545DC. The Dante
audio-over-Ethernet media networking technology is
used to transport the send and receive audio chan-
nels associated with the two single-channel party-line
(PL) circuits. The Model 545DC’s two hybrid circuits
with automatic nulling action provide good separation
of send and receive audio with high return loss and
excellent audio quality. (These hybrid circuits are
sometimes referred to as 2-wire to 4-wire converters.)
The Model 545DC’s digital audio signals are compat-
ible with all equipment that utilizes Dante technology.
An Ethernet connection is all that’s required to make
the Model 545DC part of a sophisticated, networked
audio system.
Figure 1. Model 545DC Intercom Interface front and back views
The Model 545DC can interconnect with Dante-
supported devices such as matrix intercom systems,
digital audio processors, and audio consoles. The unit
is directly compatible with RTS ADAM
®
and ODIN
®
intercom systems that support OMNEO
®
network
technology. Alternately, two Model 545DC units can
be interconnected by way of an associated Ethernet
network. The Model 545DC can also become part of
a party-line (PL) intercom system when used in con-
junction with devices such as the Models 5421 and
5422A Dante Intercom Audio Engine units from Studio
Technologies. In this way, analog party-line (PL) inter-
com circuits can become part of a high-performance
digital party-line (PL) intercom deployment.
The Model 545DC can be powered by Power-over-
Ethernet (PoE) or an external source of 12 volts
DC. The unit can provide two party-line (PL) power
sources and analog impedance termination networks,
allowing direct connection of user beltpacks such as
the Clear-Com RS-501 and RS-701 devices. A Model
545DC can also connect to one or two existing pow-
ered and terminated single-channel analog party-line
(PL) intercom circuits. The unit provides four audio
level meters that help to conrm system performance
during setup and operation. Support for transporting
industry-standard call light signals between two Model
545DC units, as well as between a Model 545DC and
other compatible units, is also provided.

Issue 1, June 2022 Model 545DC User Guide
Page 6 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
The STcontroller software application can be used to
real-time monitor and control several Model 545DC
operating parameters. In addition, two conguration
settings are performed using the application. Versions
of STcontroller are available that are compatible with
the Windows
®
and macOS
®
operating systems. They
are available, free of charge, from the Studio Tech-
nologies’ website.
Standard connectors are used for Model 545DC
party-line (PL) intercom, Ethernet, and DC power in-
terconnections. Set up and conguration of the Model
545DC is simple. A Neutrik
®
etherCON RJ45 jack
is used to interconnect with a standard twisted-pair
Ethernet port associated with a local-area network
(LAN). This connection can provide both PoE power
and bidirectional digital audio. LEDs provide status
indications of the Ethernet and Dante connections.
The unit’s lightweight aluminum enclosure is intended
for desk or tabletop use. Optional mounting kits allow
one or two Model 545DC units to be mounted in one
space (1U) of a standard 19-inch rack enclosure.
Applications
There are three main ways the Model 545DC can be
used in applications: connecting analog party-line
(PL) intercom circuits into Dante-based intercom
applications, adding party-line (PL) intercom support
for matrix intercom systems, and linking two stand-
alone analog party-line intercom circuits. The Model
545DC’s Dante transmitter (output) and receiver
(input) channels can be connected to Dante-based
digital PL intercom circuits. These circuits would typ-
ically be created using devices such as the Studio
Technologies’ Models 5421 or 5422A Dante Intercom
Audio Engines. This would allow legacy analog party-
line intercom equipment to become part of contempo-
rary digital intercom applications. The resultant audio
quality for both the analog and Dante-base PL should
be excellent.
Ports on matrix intercom systems that support Dante,
such as the RTS ADAM and ODIN with OMNEO, can
be routed to the Model 545DC’s Dante transmitter
(output) and receiver (input) channels. The Model
545DC’s circuitry will then convert these signals
into two single-channel analog party-line intercom
circuits. In this way, adding analog party-line support
will be a simple task. The Model 545DC can also be
used with matrix intercom systems that don’t support
Dante. An external analog-to-Dante interface can be
used to convert “4-wire” analog intercom resources to
Dante channels. For example, the Model 544D Audio
Interface from Studio Technologies is well suited to
function with matrix intercom systems. Once in the
Dante digital domain, these audio channels can be in-
terconnected with the Model 545DC’s Dante receiver
(input) and transmitter (output) channels.
Separate single-channel analog party-line (PL)
intercom circuits can easily be interconnected using
two Model 545DC Interfaces. On each end, a Model
545DC is connected to one or two PL circuits as well
as to the Dante network. The Dante Controller soft-
ware application is used to route (subscribe) the audio
channels between the two Model 545DC units. (The
physical distance between units will only be limited by
the deployment of the LAN’s subnet.) That’s it — noth-
ing else is required to achieve excellent performance.
The Model 545DC can also be used to “bridge”
(interconnect) one or two single-channel party-line
intercom circuits with a 2-channel party-line intercom
circuit. This involves using a Model 545DC to support
the single-channel circuits and a Studio Technolo-
gies’ Model 545DR Intercom Interface to support
the 2-channel party-line intercom circuit. The Model
545DR is a “cousin” of the Model 545DC and supports
one 2-channel party-line intercom circuit rather than
two singe-channel circuits. This 2-channel circuits,
typically supported by equipment from RTS, are com-
monly used in broadcast applications.
Party-Line Interface
As previously discussed, the Model 545DC’s two
party-line intercom interfaces are optimized for con-
nection with two single-channel party-line intercom
circuits or groups of single-channel user devices.
(While the Model 545DC will also function in a limited
manner with 2-channel RTS TW circuits, the Model
545DR Intercom Interface is the much-preferred
choice.) A party-line active detection function en-
sures that should a user beltpack or active party-line
intercom circuit not be connected the Model 545DC’s
interface circuitry will remain stable. This unique fea-
ture makes certain that objectionable audio signals,
including oscillations and “squeals,” won’t be sent to
other Dante-enabled devices.

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 7
Model 545DC
INTERCOM INTERFACE
A significant capability of the Model 545DC’s two
party-line interfaces is their ability to supply power
and a 200 ohms AC termination to “create” two inde-
pendent intercom circuits. Each 28 volts DC output
can power a moderate number of devices such as
user beltpacks. With up to 150 milliamperes (mA) of
current available, a typical entertainment application
could connect up to three RS-501 or ve RS-701 belt-
packs to each of the Model 545DC’s two interfaces. In
many applications, this can eliminate the need for an
external intercom power supply, reducing total system
cost, weight, and required mounting space. The power
supply outputs are monitored for over-current and
short-circuit conditions. Under rmware (embedded
software) control the outputs will automatically cycle
o󰀨 and on to help prevent damage to the circuitry and
connected equipment.
Dante Audio-over-Ethernet
Audio data is sent to and from the Model 545DC
using the Dante audio-over-Ethernet media network-
ing technology. Audio signals with a sample rate of
48 kHz and a bit depth of up to 24 are supported.
Audio transmitter (output) and receiver (input) chan-
nels on associated Dante-enabled devices can be
routed (subscribed) to the Model 545DC using the
Dante Controller application. This makes it simple
to select the way in which a Model 545DC ts into a
specic application.
Analog Hybrids with Auto Nulling
Two circuits, referred to as “hybrids,” interface the
Dante transmitter (output) and receiver (input) chan-
nels with the two party-line channels. The hybrids
provide low noise and distortion, good frequency
response, and high return-loss (“nulling”), even when
presented with a wide range of party-line conditions.
Unlike telephone-line (“POTS”) oriented DSP-based
hybrid circuits, the Model 545DC’s analog circuitry
maintains extended frequency response. With a
passband of 100 Hz on the low end and 8 kHz on the
high end, natural-sounding voice signals can be sent
to and received from a party-line circuit.
The Model 545DC’s sophisticated hybrid auto nulling
function uses a combination of digital and analog
circuitry under microprocessor control to achieve
signicant trans-hybrid loss. This return-loss “null”
is achieved by making a series of rmware-directed
adjustments to account for the resistive, inductive, and
capacitive conditions that are present on the connect-
ed party-line cabling and user devices. Whenever one
of the Model 545DC’s auto null buttons is pressed,
or the STcontroller application is used, digital circuitry
adjusts the associated hybrid to achieve its maximum
return-loss in under 15 seconds. While the nulling
process is automatic, it only takes place upon user
request. The resulting null parameters are stored in
non-volatile memory.
Pro Audio Quality
The Model 545DC’s audio circuitry was designed
in the spirit of professional audio equipment rather
than that found in typical party-line intercom gear.
High-performance components are used throughout,
providing low-distortion, low-noise, and high head-
room. Using active lters, the frequency response of
the audio channels is limited to nominally 100 Hz to
8 kHz. This range was selected to provide excellent
performance for human speech while maximizing
the ability of the hybrid circuits to create substantial
“nulls.”
Audio Meters
The Model 545DC contains two sets of 5-segment
LED level meters. Each set of two meters displays the
level of the signals being sent to and received from
a party-line interface. At the time of installation and
setup the meters are invaluable in helping to conrm
correct operation. During normal operation the meters
o󰀨er rapid conrmation of audio signals owing in to
and out of the Model 545DC unit.
Status Display
LED indicators are provided on the Model 545DC’s
front panel, o󰀨ering a status indication of the party-
line power sources, party-line activity, and auto null
functions. Two other LEDs o󰀨er a direct indication of
what source or sources of power are connected to
the Model 545DC. The STcontroller application also
provides a real-time “virtual” status display of the unit’s
PL power sources, PL activity, and auto null functions.
Call Light Support
Typical single-channel party-line intercom circuits
provide a call light function by way of a DC voltage
applied to the audio path. The Model 545DC can de-
tect such call light activity, converting it to a 20 kHz
audio tone which is then transported over the Dante

Issue 1, June 2022 Model 545DC User Guide
Page 8 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
audio path. A Model 545DC unit at the “far end” will
detect the “call” audio tone and regenerate it as a DC
voltage on the party-line intercom audio path. This
allows full “end-to-end” call light support between two
Model 545DC units. It also allows a Model 545DC to
send and receive call light status with an intercon-
nected Model 545DR Intercom Interface. The Model
545DR is typically used with the RTS TW-series of
two-channel party-line user beltpacks, including the
popular BP-325.
Ethernet Data, PoE, and DC Power
Source
The Model 545DC connects to a local area data net-
work (LAN) using a standard 100 Mb/s twisted-pair
Ethernet interface. The physical interconnection is
made by way of a Neutrik etherCON RJ45 jack. While
compatible with standard RJ45 plugs, an etherCON
jack allows a ruggedized and locking interconnection
for harsh or high-reliability environments. The Model
545DC’s operating power can be provided by way of
the Ethernet interface using the Power-over-Ethernet
(PoE) standard. This allows fast and e󰀩cient intercon-
nection with the associated data network. To support
PoE power management, the Model 545DC’s PoE
interface reports to the power sourcing equipment
(PSE) that it is a class 3 (mid power) device. The unit
can also be powered using an external source of 12
volts DC.
For redundancy, both power sources can be connect-
ed simultaneously. An internal switch-mode power
supply ensures that all Model 545DC features, in-
cluding party-line intercom circuit power, are available
when the unit is powered by either source. Four LEDs
on the back panel display the status of the network
connection, Dante interface, and PoE power source.
Simple Installation
The Model 545DC uses standard connectors to allow
fast and convenient interconnections. An Ethernet
signal is connected using a Neutrik etherCON RJ45
jack. If Power-over-Ethernet (PoE) is available opera-
tion will commence immediately. An external 12 volts
DC power source can also be connected by way of
a 4-pin female XLR connector. Party-line intercom
connections are made using two 3-pin male XLR con-
nectors. The Model 545DC is housed in a rugged yet
lightweight aluminum enclosure that is designed to be
“eld tough.” It can be used as a standalone portable
unit, supporting what’s known in the broadcast world
as “throw-down” applications. Rack-mounting option
kits are available that allow one or two Model 545DC
units to be mounted in one space (1U) of a standard
19-inch rack enclosure.
Future Capabilities and Firmware
Updating
The Model 545DC was designed so that its capa-
bilities and performance can easily be enhanced in
the future. A USB receptacle, located on the Model
545DC’s back panel, allows the application rmware
(embedded software) to be updated using a USB
ash drive. To implement its Dante interface the Model
545DC uses the UltimoX2™ integrated circuit from
Audinate. The rmware in this integrated circuit can
be updated via the Ethernet connection helping to
ensure that its capabilities remain up to date.
Getting Started
In this section, a location will be selected for the
Model 545DC. If desired, an optional installation kit
will be used to mount the unit into a panel cutout, wall
surface, or equipment rack. Signal interconnections
will be made using the unit’s back-panel connectors.
Connections to one or two existing party-line inter-
com circuits or one or more party-line user devices
will be made using the 3-pin XLR connectors. An
Ethernet data connection, typically which includes
Power-over-Ethernet (PoE) capability, will be made
using a standard RJ45 patch cable. A 4-pin XLR
connector allows connection of a 12 volts DC power
source.
What’s Included
Included in the shipping carton are a Model 545DC
Intercom Interface and instructions on how to obtain
an electronic copy of this guide. An optional instal-
lation kit allows a Model 545DC to be mounted in a
rectangular opening in a tabletop or attached to a at
surface. If one or two Model 545DC units are going to
be mounted in a 19-inch equipment rack then having
another of the optional rack-mount installation kits is
required. If an installation kit was purchased it would
typically have been shipped in a separate carton. As
a device that can be powered by Power-over-Ethernet
(PoE) or an external source of 12 volts DC, no power

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 9
Model 545DC
INTERCOM INTERFACE
source is included. (A compatible power supply, the
Studio Technologies’ PS-DC-02, is available as an
option.)
Locating the Model 545DC
Where to locate a Model 545DC will depend on being
able to access the associated party-line circuits or
wiring provided for the desired user devices. In addi-
tion, the unit must be located such that connection to
the designated Ethernet signal is also possible. The
Model 545DC is shipped as a self-contained “throw-
down” unit suitable for portable use or placement in
a semi-permanent location. Installed on the bottom
of the chassis are screw-a󰀩xed “bump on” protec-
tors (also known as rubber “feet”). These are useful
if the unit is going to be placed on a surface where
scratching of either the Model 545DC’s enclosure
or the surface material could take place. However, if
applicable the “feet” can be removed when installation
in a panel cutout, wall mount, or rack enclosure is
going to be performed.
Once the unit’s physical location has been established
its assumed that the twisted-pair Ethernet cabling will
be within 100-meters (325-feet) of the Ethernet port
on an associated network switch. It this is not the
case, then the overall length limit can be overcome
by using a ber-optic interconnection between the
Model 545DC’s-related-Ethernet switch and anoth-
er Ethernet switch that’s part of the application’s
local-area-network (LAN). With a ber interconnect
there’s no reason why a Dante-supported LAN can’t
be distributed over many miles or kilometers.
Mounting Options
Panel Cutout or Surface Mounting One
Model 545DC Unit
Installation kit RMBK-10 allows one Model 545DC to
be mounted in a panel cutout or onto a at surface.
The kit contains two standard-length brackets and four
6-32 thread-pitch Phillips-head machine screws. Refer
to Appendix B for a visual explanation.
Get ready to install the kit by rst removing the four
machine screws and associated “bump on” protectors
from the bottom of the Model 545DC’s chassis. They
are removed using a #1 Phillips screwdriver. Store the
four machine screws and four “bump on” protectors
for possible later use.
To prepare the unit to mount in a cutout or other
opening in a panel, use a #2 Phillips screwdriver
and two 6-32 machine screws to attach one of the
standard-length brackets onto the left side (when
viewed from the front) of the Model 545DC’s enclo-
sure. Orient the standard-length bracket such that its
front is parallel to the Model 545DC’s front panel. The
screws will mate with the threaded fasteners that can
be seen on the side of the Model 545DC’s enclosure,
near the front of the unit. Using two additional 6-32
machine screws, attach the other standard-length
bracket onto the right side of the Model 545DC’s
enclosure.
Once the two standard-length brackets have been
installed the Model 545DC will be ready to be mount-
ed into an opening. Secure the unit into the top left
and right edges of the opening using two mounting
screws per side.
To prepare the unit to be mounted onto a at surface
simply requires the standard-length brackets be
attached to the Model 545DC at 90 degrees from how
they are mounted for use in a panel cutout. Use a #2
Phillips screwdriver and two 6-32 machine screws to
attach one of the standard-length brackets onto the
left side (when viewed from the front) of the enclosure.
Orient the bracket such that its front is parallel with
the top surface of the Model 545DC’s enclosure. The
screws will mate with the threaded fasteners that can
be seen on the side of the Model 545DC’s enclosure,
near the front of the unit. Following the same orienta-
tion, use two additional 6-32 machine screws to attach
the other standard-length bracket onto the right side
of the Model 545DC’s enclosure.
Once the two standard-length brackets have been
installed the Model 545DC will be ready to be mounted
onto a at surface. Secure the unit to the surface using
two mounting screws per side.
Left- or Right-Side Rack Mounting One
Model 545DC Unit
Installation kit RMBK-11 allows one Model 545DC to
be mounted in the left or right side of one space (1U)
of a standard 19-inch rack enclosure. The kit contains
one standard-length bracket, one long-length brack-
et, and four 6-32 thread-pitch Phillips-head machine
screws. Refer to Appendix C for a visual explanation.

Issue 1, June 2022 Model 545DC User Guide
Page 10 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
Get ready to install the kit by removing the four
machine screws and associated “bump on” protectors
from the bottom of the Model 545DC’s chassis. They
are removed using a #1 Phillips screwdriver. Store the
four machine screws and four “bump on” protectors
for possible later use.
To prepare the unit to mount in the left side of a rack
enclosure, use a #2 Phillips screwdriver and two
6-32 machine screws to attach the standard-length
bracket onto the left side (when viewed from the
front) of the enclosure. The screws will mate with the
threaded fasteners that can be seen on the side of the
Model 545DC’s enclosure, near the front of the unit.
Using two additional 6-32 machine screws, attach the
long-length bracket onto the right side of the Model
545DC’s enclosure.
To prepare the unit to mount in the right side of a rack
enclosure, use a #2 Phillips screwdriver and two 6-32
machine screws to attach the long-length bracket onto
the left side of the enclosure. Using two additional
6-32 machine screws, attach the standard-length
bracket onto the right side of the Model 545DC’s
enclosure.
Once the standard-length and long-length brackets
have been installed the Model 545DC will be ready
to be mounted into the designated equipment rack.
One space (1U or 1.75 vertical inches) in a standard
19-inch equipment rack is required. Secure the unit
into the equipment rack using two mounting screws
per side.
Rack-Mounting Two Model 545DC Units
Installation kit RMBK-12 is used to allow two Model
545DC units to be mounted in one space (1U) of a
standard 19-inch equipment rack. The kit can also
be used to mount one Model 545DC and one other
Studio Technologies product that is compatible with
the RMBK-12, such as the Model 545DR Intercom
Interface or the Model 5421 Dante Intercom Audio
Engine. The RMBK-12 installation kit contains two
standard-length brackets, two joiner plates, eight 6-32
thread-pitch Phillips-head machine screws, and two
2-56 thread-pitch Torx™ T7 thread-forming machine
screws. Refer to Appendix D for a visual explanation.
Get ready to install the kit by removing the four ma-
chine screws and associated “bump on” protectors
from the bottom of each chassis. They are removed
using a #1 Phillips screwdriver. Store the eight
machine screws and eight “bump on” protectors for
possible later use.
With assistance from a #2 Phillips screwdriver, use
two of the 6-32 machine screws to attach one of the
standard-length brackets onto the left side (when
viewed from the front) of one of the Model 545DC
units. The screws will mate with the threaded fasten-
ers that can be seen on the side of the Model 545DC’s
enclosure, near the front of the unit. Using two more
of the 6-32 machine screws, attach one of the joiner
plates onto the right side of that same Model 545DC
unit.
Again using two of the 6-32 machine screws, attach
the second standard-length bracket onto the right side
of the second Model 545DC or another compatible
unit. Using the nal two 6-32 machine screws, attach
the second joiner plate onto the left side of the sec-
ond Model 545DC or other compatible unit with an
orientation of 180 degrees from the way in which the
rst plate was installed.
To complete the assembly, “join” the units together
by sliding each joiner plate through the other. The
grooves in each joiner plate will carefully align with
each other and form a relatively tight bond. Line up
the two units so that the front panels form a common
plane. With the aid of a Torx T7 screwdriver, use the
two 2-56 Torx machine screws to secure the two
joiner plates together. The screws should t snugly
into the small openings formed by the mating of the
two joiner plates.
The 2-unit assembly is now ready to be mounted
into the designated equipment rack. One space (1U
or 1.75 vertical inches) in a standard 19-inch equip-
ment rack is required. Secure the assembly into the
equipment rack using two mounting screws per side.
Center Rack Mounting One Model 545DC
Unit
Installation kit RMBK-13 allows one Model 545DC
to be mounted in the center of one space (1U) of a
standard 19-inch rack enclosure. The kit contains two
medium-length brackets and four 6-32 thread-pitch
Phillips-head machine screws. Refer to Appendix E
for a visual explanation.
Get ready to install the kit by removing the four
machine screws and associated “bump on” protectors
from the bottom of the Model 545DC’s chassis. They

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 11
Model 545DC
INTERCOM INTERFACE
are removed using a #1 Phillips screwdriver. Store the
four machine screws and four “bump on” protectors
for possible later use.
To prepare the unit to mount in the center of a rack
enclosure, use a #2 Phillips screwdriver and two 6-32
machine screws to attach one of the medium-length
brackets onto the left side (when viewed from the
front) of the enclosure. The screws will mate with the
threaded fasteners that can be seen on the side of the
Model 545DC’s enclosure, near the front of the unit.
Using two additional 6-32 machine screws, attach the
other medium-length bracket onto the right side of the
Model 545DC’s enclosure.
Once the two medium-length brackets have been in-
stalled the Model 545DC will be ready to be mounted
into the designated equipment rack. One space (1U or
1.75 vertical inches) in a standard 19-inch equipment
rack is required. Secure the unit into the equipment
rack using two mounting screws per side.
Ethernet Connection with PoE
An Ethernet connection that supports 100BASE-TX
(100 Mb/s over twisted-pair) is required for Model
545DC operation. A 10BASE-T connection is not
su󰀩cient; a 1000BASE-T (GigE) connection is not
supported unless it can automatically “fall back” to
100BASE-TX operation. An Ethernet connection that
supports Power-over-Ethernet (PoE) is preferred
as it will also provide operating power for the Model
545DC. To support a PoE Ethernet switch (PSE) that
includes power management capability the Model
545DC will enumerate itself as a PoE class 3 device.
A 100BASE-TX Ethernet connection is made by way
of a Neutrik etherCON RJ45 jack that is located on
the back panel of the Model 545DC. This allows con-
nection by way of a cable-mounted etherCON plug
or a standard RJ45 plug. A crossover cable will never
be required as the Model 545DC’s Ethernet interface
supports auto MDI/MDI-X. Per the Ethernet standard,
the Ethernet Switch-to-Ethernet Device length limita-
tion for twisted-pair cabling is 100-meters (325-feet).
External 12 Volt DC Input
An external source of 12 volts DC can be connected
to the Model 545DC by way of a 4-pin male XLR
connector which is located on the unit’s back panel.
While the stated requirement for the external source
is nominally 12 volts DC, correct operation will take
place over a 10 to 18 volts DC range. The Model
545DC requires a maximum current of 1.0 amperes
for correct operation. The DC source should be ter-
minated on a 4-pin female XLR connector with pin 1
negative (–) and pin 4 positive (+); pins 2 and 3 should
remain unterminated. Purchased as an option, the
PS-DC-02 power supply, available from Studio Tech-
nologies, is directly compatible. Its AC mains input
allows connection to 100-240 volts, 50/60 Hz and has
a 12 volts DC, 1.5 amperes maximum output that is
terminated on a 4-pin female connector.
As previously discussed, an Ethernet connection that
provides Power-over-Ethernet (PoE) capability can
serve as the Model 545DC’s power source. Alternate-
ly, an external 12 volts DC source can be connected.
For redundancy, both PoE and an external 12 volts
DC source can be connected at the same time. If
both PoE and an external 12 volts DC source are
connected, power will be drawn only from the PoE
supply. If the PoE source becomes inoperative the
12 volts DC source will provide the Model 545DC’s
power with no interruption in operation. (Of course, if
both PoE and Ethernet data support are lost that is a
very di󰀨erent situation!)
Party-Line Intercom Connections
The Model 545DC’s two single-channel party-line
intercom interfaces are designed to independently
function in two distinct ways. They can be connected
to independent “powered” single-channel party-line
intercom circuits. Alternately, they can be connect-
ed directly to party-line intercom user devices.
A single-channel party-line intercom circuit, often
associated with equipment from Clear-Com, will have
DC power and one audio channel on a 3-pin XLR
connector. These connectors will be wired such that
common is on pin 1, 28 to 32 volts DC is on pin 2,
and talk audio is present on pin 3. A single-channel
party-line intercom circuit will also typically include
an impedance-generating network that provides a
200 ohms audio (AC) load from pin 3 to pin 1. (And in
some cases, a DC “call” signal may, when applicable,
also be present on pin 3.) When the Model 545DC’s
party-line interface is connected to an existing inter-
com circuit it will act, from an audio standpoint, similar
to that of a standard party-line intercom user device.
The Model 545DC’s interface won’t draw (use) any
DC power from pin 2 although it is capable of applying
DC “call” voltage on pin 3.

Issue 1, June 2022 Model 545DC User Guide
Page 12 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
The Model 545DC’s two party-line interfaces can
also serve to create two “mini” intercom circuits. They
each provide an intercom power source along with a
200 ohms impedance generator, allowing a limited
number of single-channel intercom user devices to
be directly connected. Each of the Model 545DC’s
intercom interfaces can provide 28 volts DC on pin 2
with a maximum current of 150 mA. While relatively
modest, this amount of power can be very useful but
requires that the type and number of connected user
devices be selected appropriately. Many entertain-
ment applications use the legacy Clear-Com RS-501
beltpack and a Model 545DC intercom circuit can
directly support up to three of them. Applications that
utilize the newer and more energy e󰀩cient Clear-Com
RS-701 should allow up to ve to be connected and
powered by each Model 545DC intercom circuit. Wir-
ing from the Model 545DC intercom interface’s 3-pin
male XLR connectors to user devices require that a
1-to-1, 2-to-2, 3-to-3 wiring scheme on the mating
3-pin XLR connectors be maintained.
Compatibility with 2-Channel Intercom
Systems
As previously discussed, the Model 545DC is de-
signed to directly support two single-channel party-line
intercom circuits and groups of user devices. It’s also
possible that applications that involve a 2-channel
party-line intercom circuit and user devices (typically
associated with the RTS TW-series of products) can
be supported. These circuits and devices typically uti-
lize a common connection on pin 1, 28 to 32 volts DC
and channel 1 audio on pin 2, and channel 2 audio on
pin 3. When a 2-channel circuit or device is connected
to a Model 545DC, only the device’s channel 2 will
be active; the device’s channel 1 will not be active.
A better means to support these 2-channel circuits
and devices is to use the Studio Technologies’ Model
545DR Intercom Interface. This unit, the “cousin” of
the Model 545DC, is optimized for 2-channel party-line
intercom applications. Rather than providing two
single-channel interfaces the Model 545DR provides
one 2-channel interface. Detailed information about
the Model 545DR is available on the Studio Technol-
ogies’ website.
Dante Conguration
To integrate the Model 545DC into an application re-
quires that a number of Dante-related parameters be
congured. These conguration settings will be stored
in non-volatile memory within the Model 545DC’s
Dante interface circuitry. Conguration will typically
be done using the Dante Controller software appli-
cation which is available for download free of charge
at audinate.com. Versions of Dante Controller are
available to support the Windows and macOS per-
sonal computer operating systems. The Model 545DC
uses the UltimoX2 2-input/2-output integrated circuit
to implement its Dante interface. The Model 545DC’s
Dante interface is compatible with the Dante Domain
Manager (DDM) software application.
Audio Routing
Two Dante transmitter (output) channels on associ-
ated equipment should be routed (subscribed) to the
Model 545DC’s two Dante receiver (input) channels.
The Model 545DC’s two Dante transmitter (output)
channels should be routed (subscribed) to two Dante
receiver (input) channels on associated equipment.
This achieves audio interconnection of the Model
545DC’s two party-line intercom channels with the
Dante network and associated Dante device or
devices.
Within Dante Controller a “subscription” is the term
used for routing a transmitter channel or ow (a group
of up to four output channels) to a receiver channel or
ow (a group of up to four input channels). The num-
ber of transmitter ows associated with an UltimoX2
integrated circuit is limited to two. These can either be
unicast, multicast, or a combination of the two. If the
Model 545DC’s transmitter (output) channels need to
be routed using more than two ows it’s possible that
an intermediary device, such as the Studio Technolo-
gies’ Model 5422A Dante Intercom Audio Engine, can
be used to “repeat” the signals.
Model 545DC units will typically be used in one
of two common congurations: “point-to-point” or in
association with other Dante-enabled equipment. The
rst conguration will utilize two Model 545DC units
that “work” together to link two physical locations. At
each location there will either be an existing party-line
intercom circuit or a set of user intercom devices
(such as beltpacks). The two Model 545DC units will

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 13
Model 545DC
INTERCOM INTERFACE
operate “point-to-point,” interconnecting by way of the
associated Ethernet network. To implement this appli-
cation is very simple. The From Party-Line Channel A
channel on each unit would be routed (subscribed) to
the To Party-Line Channel A channel on the other unit.
And the From Party-Line Channel B channel on each
unit would be routed (subscribed) to the To Party-Line
Channel B channel on the other unit.
The other typical application will have one Model
545DC connected to an existing party-line intercom
circuit or a set of user devices. Then the unit’s Dan-
te audio channels would be routed (subscribed) to
the Dante transmitter (output) and receiver (input)
channels on associated Dante-enabled equipment.
An example of this equipment could be the RTS
ADAM matrix intercom system that provides Dante
interconnection capability using its OMNEO interface
card. The audio channels on the Model 545DC would
be routed (subscribed) to and from audio channels
on the OMNEO card. Other equipment that supports
Dante, such as audio consoles or audio interfaces
(Dante-to-MADI, Dante-to-SDI, etc.), can have their
audio channels routed (subscribed) to and from a
Model 545DC.
Device and Channel Names
The Model 545DC has a default Dante device name
of ST-545DC- followed by a unique su󰀩x. (A technical
reason prevents the default name to be the preferred
ST-M545DC- (an “M” included). But that can be added
by the user.) The su󰀩x identies the specic Model
545DC that is being congured. The su󰀩x’s actual
alpha and/or numeric characters relate to the MAC
address of the unit’s UltimoX2 integrated circuit. The
unit’s two Dante transmitter (output) channels have
default names of From Ch A and From Ch B. The
unit’s two Dante receiver (input) channels have default
names of To PL Ch A and To PL Ch B. Using Dante
Controller, the default device and channel names can
be revised as appropriate for the specic application.
Device Conguration
The Model 545DC only supports an audio sample
rate of 48 kHz with no pull-up/pull-down values avail-
able. The audio encoding is xed for PCM 24. Device
Latency and Clocking can be adjusted if required but
the default value is typically correct.
Network Conguration – IP
Address
By default, the Model 545DC’s Dante IP address and
related network parameters will be determined auto-
matically using DHCP or, if not available, the link-local
network protocol. If desired, Dante Controller allows
the IP address and related network parameters to be
manually set to a xed (static) conguration. While
this is a more-involved process than simply letting
DHCP or link-local “do their thing,” if xed addressing
is necessary then this capability is available. In this
case, it’s highly recommended that a unit be physically
marked, e.g., directly using a permanent marker or
“console tape,” with its specic static IP address. If
knowledge of a Model 545DC’s IP address has been
misplaced there is no reset button or other method to
easily restore the unit to a default IP setting.
AES67 Conguration – AES67
Mode
The Model 545DC can be configured for AES67
operation. This requires the AES67 Mode to be set for
Enabled. By default, AES67 mode is set for Disabled.
Note that in the AES67 mode the Dante transmitter
(output) channels will function in multicast; unicast is
not supported.
Model 545DC Clocking Source
While technically the Model 545DC can serve as
a Leader clock for a Dante network (as can all
Dante-enabled devices) in virtually all cases the unit
will be configured to receive “sync” from another
device. As such, the check box for Preferred Leader
associated with the Model 545DC would not want to
be enabled.

Issue 1, June 2022 Model 545DC User Guide
Page 14 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
Model 545DC Conguration
The STcontroller software application is used to congure two Model 545DC functions, call light support, and
PL active detection. (STcontroller also allows real-time display and control of other Model 545DC functions.
These functions will be detailed in the Operation section.) No DIP switch settings or other local actions are used
to congure the unit. This makes it imperative that STcontroller be available for convenient use on a personal
computer that’s connected to the related LAN.
Installing STcontroller
STcontroller is available free of charge on the Studio Technologies’ website (studio-tech.com). Versions are
available that are compatible with personal computers running selected versions of the Windows and macOS
operating systems. If required, download and install STcontroller onto a designated personal computer. This
personal computer must be on the same local area network (LAN) and subnet as the one or more Model 545DC
units that are to be congured. Immediately after starting STcontroller the application will locate all the Studio
Technologies’ devices that it can control. The Model 545DC units that can be congured will appear in the
device list. Use the Identify command to allow easy recognition of a specic Model 545DC unit. Double-clicking
on a device name will cause the associated conguration menu to appear. Review the current conguration
and make any changes that are desired.
Conguration changes made using STcontroller will be immediately reected in the unit’s operation; no Model
545DC reboot is required. As an indication that a conguration change has been made the two LEDs associ-
ated with input power, labeled DC and PoE, on the Model 545DC’s front panel will ash in a distinctive pattern.

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 15
Model 545DC
INTERCOM INTERFACE
System – Call Light Support
Choices are O and On.
In STcontroller, the Call Light Support conguration
function allows the call light support function to be
enabled or disabled as desired. When the function is
On, the call light support function is enabled. When the
Call Light Support conguration is selected for O the
function is disabled. For most applications the call light
support function should remain enabled. Only special
circumstances would merit disabling the function.
System – PL Active Detection
Choices are O and On.
The Model 545DC’s current detection function for a
party-line interface will be active when both the local
power source has been enabled and the PL Active
Detection conguration has been selected for On.
When these two parameters are selected a minimum
current of 5 mA (nominal) must be drawn from pin 2
of a PL interface for the Model 545DC to recognize a
“PL active” condition. When this minimum current con-
dition is met the LED labeled Active for that specic
channel will light green, the PL Active status icon on
the STcontroller’s menu page will show green, and the
Dante transmitter (output) audio path will be active.
Having the PL Active Detection function enabled is
appropriate for most applications, helping to main-
tain the most stable audio performance. Only when
su󰀩cient current is drawn from pin 2 of an interface
will audio from that PL channel be sent out the Dante
transmitter (output) channel.
When the PL Active Detection configuration is
selected to O (disabled), no minimum current draw is
required on pin 2 of the either of the PL interfaces for
their Active LEDs to be lit, the STcontroller graphics
icons to display green, and the Dante transmitter (out-
put) channels to be active. However, only in special
situations would it be appropriate for the PL Active
Detection conguration be selected for O󰀨.
An example where O󰀨 would be appropriate would be
the case where a Model 545DC is being used with a
hypothetical device that has a single-channel party-
line interface that doesn’t draw DC power. This unit
might expect to be connected to an intercom circuit
using a 3-pin XLR connector with common on pin 1,
DC power on pin 2, and audio pin 3. The Model 545DC
can provide a compatible PL circuit when its local
power source is enabled. But a problem can arise as
this unit might not draw current from pin 2 of the Model
545DC’s PL intercom circuit. It may not function in the
same manner as would a typical PL intercom beltpack
or user device. It wouldn’t use power from the PL
connection, instead using its internal power source for
operation. In this case, the Model 545DC’s party-line
interface would not supply current, the Active LED
would not light, the active icon in STcontroller would
not turn green, and the Dante transmitter (output)
audio path would not be enabled. Users of the device
would receive Model 545DC Dante receiver (input)
audio but would not send audio out the Dante trans-
mitter (output) channel. Using STcontroller to turn o󰀨
the PL Active Detection function would resolve this
issue. Even though no DC current would be sup-
plied by the Model 545DC’s PL interface, the Dante
transmitter (output) channel would be enabled and
successful PL interface operation could take place.
When a Model 545DC party-line intercom circuit has
been set to not provide local power the PL Active
Detection function works in a slightly di󰀨erent way.
Only if a DC voltage of approximately 18 or greater
is present on pin 2 of the PL interface will the Model
545DC recognize that a valid PL interconnection
has been made. In this case, the channel’s Active
LED on the front panel will light green, the virtual
button in STcontroller will light green, and the Dante
transmitter (output) audio channel for that interface
will be active. When the PL Active Detection function
is disabled, monitoring of DC voltage on pin 2 of the
Model 545DC’s PL interfaces will not take place. In
this situation, the Active LEDs on the Model 545DC’s
front panel will always be lit, the virtual indicators in
STcontroller would be lit, and the Dante transmitter
(output) audio channels will be active. The practical
application of this specic conguration has not been
determined, but it’s ready should the need arise!

Issue 1, June 2022 Model 545DC User Guide
Page 16 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
Operation
At this point, the Model 545DC should be ready for
use. The party-line intercom and Ethernet connec-
tions should have been made. Depending on the
application, an external source of 12 volts DC power
may also have been made. (A 12 volts DC power
source is not included with the Model 545DC. One
can be purchased as an option.) The Dante receiver
(input) and transmitter (output) channels should have
been routed (subscribed) using the Dante Controller
software application. Normal operation of the Model
545DC can now begin.
On the front panel, multiple LEDs provide an indication
of the unit’s operating status. In addition, two push-
button switches are provided to select the on/o󰀨 status
of the local power mode functions as well as activat-
ing the auto null functions. The STcontroller software
application can be used to observe the status of some
of the unit’s operating conditions. Virtual pushbutton
switches associated with STcontroller also allow con-
trol of the on/o󰀨 status of the local power modes in
addition to initiating the auto null functions.
Initial Operation
The Model 545DC will begin its initial functioning
a few seconds after its power source is connected.
As previously discussed, the unit’s power can be
provided by Power-over-Ethernet (PoE) or an external
source of 12 volts DC. If both are connected the PoE
source will power the unit. Should PoE subsequently
no longer be available operation will continue using
the external 12 volts DC source.
Upon Model 545DC power up many of the status and
meter LEDs on the front and back panels will activate
in test sequences. On the back panel, the LED as-
sociated with the USB receptacle, labeled Firmware
Update, will light green for a few seconds. Soon after
that the Dante SYS and Dante SYNC LEDs will light
red. After a few seconds they will begin indicating the
operating status of the Dante interface, turning green
as valid conditions are established. The Ethernet
LINK/ACT LED, also located on the back panel, will
begin to ash green in response to data owing into
and out of the Ethernet interface.
On the front panel, the input power, auto null, party-
line intercom circuit status, and level meter LEDs
will light in a rapid test sequence. The Model 545DC
will now begin normal operation. The exact manner
in which the LINK/ACT, SYS, and SYNC LEDs (all
located on the back panel below the etherCON RJ45
jack) light will depend on characteristics related to
the connected Ethernet signal and the conguration
of the unit’s Dante interface. Details will be covered
in the next paragraph. On the front panel, the user is
presented with two pushbutton switches, two input
power status LEDs, four party-line intercom circuit
status LEDs, two auto null LEDs, and four 5-segment
LED level meters. These resources are simple to
understand and control, as will be described in the
following paragraphs.
Ethernet and Dante Status LEDs
Three status LEDs are located below the ether-
CON RJ45 jack on the Model 545DC’s back panel.
The LINK/ACT LED will light green whenever an
active connection to a 100 Mb/s Ethernet network
has been established. It will ash in response to data
activity. The SYS and SYNC LEDs display the operat-
ing status of the Dante interface and associated net-
work. The SYS LED will light red upon Model 545DC
power up to indicate that the Dante interface is not
ready. After a short interval, it will light green to indicate
that it is ready to pass data with another Dante device.
The SYNC LED will light red when the Model 545DC
is not synchronized with a Dante network. It will light
solid green when the Model 545DC is synchronized
with a Dante network and an external clock source
(timing reference) is being received. It will slowly ash
green when this specic Model 545DC unit is part of a
Dante network and is serving as the Leader clock. (It’s
important to note that typical applications will not have
a Model 545DC unit serving as a Dante Leader clock.)
How to Identify a Specic Model
545DC
Both the Dante Controller and STcontroller software
applications offer identify commands that can be
used to help locate a specic Model 545DC. When
an identify command is selected for a specic Model
545DC unit its meter LEDs will light in a unique pat-
tern. In addition, the SYS and SYNC LEDs, located
directly below the etherCON jack on the back panel,
will slowly ash green. After a few seconds, the LED
identication patterns will cease and normal Model
545DC level meter and Dante status LED operation
will again take place.

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 17
Model 545DC
INTERCOM INTERFACE
Level Meters
The Model 545DC contains four 5-segment LED
level meters. These meters are provided as a support
aid during installation, conguration, operation, and
troubleshooting. The meters represent the strength of
the audio signals going to and coming from the two
party-line intercom circuits.
General
The meters are organized into two groups with each
group representing one channel of audio being sent
to a party-line circuit and one channel of audio being
returned by a party-line circuit. The meters are cali-
brated to reect the level in dB relative to the reference
(nominal) level of the party-line intercom circuit. The
Model 545DC’s nominal party-line level was select-
ed to be –14 dBu, matching that utilized by typical
single-channel party-line intercom circuits. (Note that
very early single-channel Clear-Com systems had a
nominal level of –20 dBu but that’s no longer true for
contemporary units.)
Each level meter contains four green LEDs and one
yellow LED. The four green LEDs indicate party-line
intercom channel signal levels that are at or below
–14 dBu. The top LED is yellow and indicates a signal
that is 6 dB or greater than the –14 dBu nominal level.
Audio signals that cause the yellow LEDs to light don’t
necessarily indicate an excessive level condition,
but do provide a warning that reducing the signal
level may be prudent. Typical operation with normal
signal levels should nd the meters lighting near their
0 point. Signal peaks may cause a yellow LED to ash.
A yellow LED that lights fully during normal operation
will indicate an excessive signal level conguration
and/or a configuration problem with associated
Dante-enabled equipment.
As an example of how the meters function, let’s review
the situation where the Channel A To meter has its
bottom three LEDs (–18, –12, and –6) lit solid and its
0 LED just barely lighting. This would indicate that a
signal with an approximate level of –14 dBu is being
sent to party-line intercom channel A. This would be
a very appropriate signal level and should provide
excellent operation. (Also note that a –14 dBu signal
that is being sent to party-line intercom channel A
would indicate that a –20 dBFS digital audio signal is
present on Dante receiver (input) channel A. This is
due to Studio Technologies’ selecting –20 dBFS as the
reference (nominal) level for Dante audio channels.)
Non-Optimal Signal Levels
If one or more of the meters consistently display levels
that are lower or higher than the 0 (reference) point it’s
possible that a conguration issue exists. This would
typically be related to incorrect settings on the equip-
ment connected to the associated Dante receiver
(input) and/or Dante transmitter (output) channels. (It
would be almost impossible for this situation to occur
if two Model 545DC units are congured “point-to-
point” as no Dante digital audio level adjustment is
provided.) With a digital matrix intercom system this
problem could be due to an incorrect conguration
having been made to a specic channel or port. For
example, the RTS/Telex/Bosch ADAM system has a
published nominal audio level of +8 dBu, but it’s not
clear how this translates into a digital audio level on
an associated Dante or OMNEO channel. (OMNEO is
the term that RTS uses to refer to their Dante ports.)
Using its AZedit conguration software it’s possible to
set the nominal level of intercom key panels or ports
to something di󰀨erent than +8 dBu. The best solution
in this case might be to adjust the associated OMNEO
(Dante-compatible) ports to achieve nominal audio
levels of –20 dBFS on the associated Dante transmit-
ter (output) and receiver (input) channels. Providing
compatible digital audio reference levels would lead
to the best performance of the Model 545DC and
associated party-line user devices.
Audio Levels and Party-Line Termination
The two From meters display the audio signal levels
coming from the two channels associated with the
Model 545DC’s party-line intercom channels A and
B. These analog signals are converted to digital and
then output on Dante transmitter (output) channels.
For a party-line intercom circuit associated with a
Model 545DC to function correctly, the impedance
(resistance to AC signals such as audio) must be
approximately 200 ohms. Typically, to achieve this
depends on a single piece of equipment providing one
audio termination per intercom channel. This termi-
nation, 200 ohms nominally, is almost always made
at the intercom power supply source. (An intercom
power supply unit typically provides both DC power
and an intercom termination network.)

Issue 1, June 2022 Model 545DC User Guide
Page 18 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
An issue may arise if the audio signal coming from the
connected party-line intercom circuit or user devices
isn’t at a su󰀩cient level such that normal meter dis-
play levels can be reached. It’s possible that another
device, such as a second intercom power supply
on the same party-line intercom circuit, can cause a
“double-termination” condition. This would result in
a party-line intercom channel impedance of approxi-
mately 100 ohms (two sources, each 200 ohms, con-
nected in parallel) which would cause a major issue.
The most evident problem would be that the intercom
channel’s nominal audio levels would attenuate (drop)
by about 6 dB (half the audio voltage). In addition, auto
null circuits, such as provided by the Model 545DC,
will not be able to obtain good separation (nulling)
performance. Removing the unwanted second ter-
mination (the second impedance of 200 ohms) is the
only e󰀨ective means of eliminating the problems.
In most cases, a double-termination issue will be
simple to solve. As an example, it’s possible that one
of the Model 545DC’s local power sources, which pro-
vide both DC power and 200 ohms termination, has
been accidentally enabled when the Model 545DC is
connected to an externally powered and terminated
party-line circuit. This would be incorrect, leading
to a “double-termination” condition. Turning o󰀨 the
Model 545DC’s local power source by pressing and
holding the appropriate auto null button or using the
STcontroller software application is all that is required.
Some intercom power supply units allow selection of
the termination impedance to be 200 or 400 ohms.
This capability is often incorporated into a 3-position
switch that also allows no termination impedance to
be applied. Ensure that the selected switch setting,
as well as the settings and deployment of other
connected equipment, results in an intercom circuit
impedance of 200 nominal for each of the two sin-
gle-channel circuits.
Power Status LEDs
Two green LEDs are located on the left side of the
front panel and are associated with operating power.
The PoE LED indicator will light whenever an Ethernet
connection with Power-over-Ethernet (PoE) capability
is connected. The DC power LED will light when-
ever an external DC voltage has been applied. The
acceptable range is 10 to 18 volts DC. If both power
sources are present both LEDs will light, however only
the PoE source will be providing the Model 545DC’s
operating power.
Party-Line Operating Mode
Selection
As discussed previously, each of the unit’s two
single-channel party-line circuits provides two operat-
ing modes. One mode is used when the Model 545DC
is required to create a party-line intercom circuit,
providing 28 volts DC and a 200 ohms termination
impedance network. In this mode, user devices such
as beltpacks can be directly supported. The associat-
ed Local Power status LED will light green when this
mode is selected. A virtual (software-based-graphics)
button that’s part of the STcontroller application will
show the text On to indicate that local power has
been enabled. The second mode allows the Model
545DC to be connected to a single-channel party-line
intercom circuit that provides both DC power and 200
ohms terminating impedance. In this mode, the unit
will perform in the same manner as a user device
and the Local Power status LED will not be lit. In this
mode, the text O󰀨 will be shown in the STcontoller’s
virtual pushbutton switch.
To change a party-line interface’s operating mode is
simple, only requiring the associated auto null push-
button switch to be pressed and held for a minimum
of two seconds. This will cause the Model 545DC’s
operating mode to change (“toggle”) from one mode
to the other. As the mode changes, the associated
Local Power status LED and STcontroller application
will display accordingly. Once the mode has changed
the pushbutton switch can then be released. The op-
erating mode can also be selected using the virtual
pushbutton switch in the STcontroller software appli-
cation. The selected operating mode will be stored in
non-volatile memory, ensuring that it will restore to that
value after a power-down/power-up cycle.
Local Power Mode Operation
When the Model 545DC’s local power mode is
enabled for an intercom circuit, the unit will provide
DC power and a 200 ohms termination impedance to
create a “standard” single-channel party-line intercom
circuit. The party-line interface will supply 28 volts
DC on pin 2 of the 3-pin XLR connectors with a max-
imum current draw of 150 mA available. This current
is su󰀩cient to power various intercom user devices
such as small user stations and beltpacks. A common

Model 545DC User Guide Issue 1, June 2022
Studio Technologies, Inc. Page 19
Model 545DC
INTERCOM INTERFACE
broadcast application may use Clear-Com RS-501
or RS-701 beltpacks. Select the connected devices
so that their total maximum current doesn’t exceed
150 mA. That’s not always the easiest gure to calcu-
late but a web search will generally nd specications
for all commonly used devices. For example, a search
nds that the ubiquitous RS-501 consumes a maxi-
mum of 50 mA of current. According to this gure, up
to three of these units can be connected to a Model
545DC. The newer RS-701 has a quiescent current
of 12 mA and an approximate maximum of 23 mA.
From this information one could estimate that up to
ve of these units can easily be supported.
When the local power mode has been enabled, the
associated Active status LED will light green when a
minimal amount of current is owing from the Model
545DC’s party-line circuit to the connected user device
or devices. This will also cause the associated virtual
LED named PL Active in the STcontroller application
to light green. This current, 5 mA nominal, provides
a party-line power source-active signal to the Model
545DC’s rmware indicating that normal operation
is taking place. The rmware, in turn, will cause the
Active status LED to light, the STcontroller application
to light its virtual LED, and the Dante transmitter (out-
put) audio channel to be in its active (unmuted) state.
(By muting the Dante transmitter (output) channel
when the intercom circuit is not active unwanted audio
signals will be prevented from passing to the outside
world when no party-line device is connected.)
Note that a setting in the STcontroller application
can disable the requirement that a current draw of
5 mA (nominal) or greater on pin 2 of a party-line
XLR connector is required for the Active status LED
to light, the virtual LED in the STcontroller application
to light green, and the transmitter (output) audio path
to be active. This function is called PL Active Detec-
tion and disabling it can be appropriate for special
applications. Refer to the Model 545DC Conguration
section for details regarding this function and how it
may be utilized.
The Model 545DC’s two party-line intercom power
supply circuits operate under rmware control. This
allows detection of fault conditions and protects the
unit’s circuitry. Upon initially enabling a party-line
intercom power supply no monitoring of the intercom
power output takes place for three seconds. This
allows a Model 545DC intercom power supply circuit
and connected intercom user device or devices to
stabilize. The associated Local Power status LED
will be lit solid and the virtual pushbutton switch in
the STcontroller application will show the text On. The
Active status LED, which responds to the status of the
DC voltage on pin 2 of the party-line interface’s 3-pin
XLR connector, will light to indicate that the output is
active. The PL Active virtual LED in STcontroller will
light green. After this initial delay, monitoring becomes
active. A fault condition is detected if the voltage on
pin 2 falls below 24 for a continuous 1-second interval.
The rmware responds to this condition by momen-
tarily turning o󰀨 the DC power source to pin 2. It will
also, as a warning, ash the associated Active status
LED and ash the virtual LED in STcontroller. After a
5-second “cool-down” interval the DC output will return
to the same condition as upon initial power up; power
is again applied to pin 2, the Active status LED will
light, the virtual PL Active LED will light green, and
monitoring won’t begin for another three seconds. A
full short-circuit condition applied to a party-line power
supply circuit will result in a continuous cycle of four
seconds on (three seconds for startup and one second
for detection) and then ve seconds o󰀨.
External Party-Line Circuit Operation
When a Local Power status LED on the front panel is
not lit and the virtual pushbutton switch in STcontroller
is labeled O󰀨 the associated Model 545DC’s party-line
interface does not provide DC power on XLR pin 2 nor
provides 200 ohms terminating impedance on XLR
pin 3. In this mode, the Model 545DC is intended to
be connected to an externally powered party-line cir-
cuit. This party-line circuit must provide the DC power
and termination impedance required to create the
party-line intercom circuit. In this mode, the Model
545DC simply serves in the same fashion as that of
another connected single-channel user device. (In
e󰀨ect, the Model 545DC would have the technical
characteristics of a non-powered user device.) When
connected to a powered party-line circuit the Model
545DC’s Active status LED will light when approxi-
mately 18 volts DC or greater is present on pin 2 of
the associated XLR connector. In addition, the
STcontroller’s PL Active virtual LED will light green.
When this condition is detected, the associated Dan-
te transmitter (output) channel is placed in its active
(non-muted) state. Otherwise, it is off (muted) to
maintain stable Model 545DC performance.

Issue 1, June 2022 Model 545DC User Guide
Page 20 Studio Technologies, Inc.
Model 545DC
INTERCOM INTERFACE
As previously described, a setting in the STcontroller
application can disable the requirement that 18 volts
DC or greater be present on pin 2 of the party-line
XLR connector for the Active status LED to light, the
PL Active virtual LED to light green, and the transmit-
ter (output) audio path to be active. This function is
called the PL Active Detection function and disabling
it can be appropriate for special applications. Refer
to the Model 545DC Conguration section for details
regarding this function and how it may be utilized.
Auto Null
The Model 545DC contains circuitry to automatically
null the hybrid network associated with each party-line
interface. This procedure separates the audio sig-
nals as they are sent to and received from the audio
channels associated with the two party-line intercom
circuits. Two pushbutton switches, located on the front
panel, are provided to activate the auto null functions,
one for each channel. Virtual (“soft”) buttons in the
STcontroller software application also allow activation
of the auto null functions. Two status LEDs, located
on the unit’s front panel, and two virtual (software-
graphics-based) LEDs provided in STcontroller pro-
vide an indication of the operation of the auto null
circuits.
To initiate auto null for a circuit rst requires that the
associated Active status LED be lit. When the oper-
ating mode is set for local power the Active status
LED will light when the required minimum amount of
current is owing from the internal power supply. Alter-
nately, when the Local Power LED is not lit the Active
status LED must be lit, indicating that su󰀩cient DC
voltage is present on pin 2 of the connected party-line
circuit. Once the Active status LED is lit, initiating the
auto null function only requires pressing and releasing
(“tapping”) the front-panel auto null button. Alternately,
the virtual button in the STcontroller application can be
used to initiate auto null. The auto null process takes
approximately 10 seconds to complete. LEDs on the
unit’s front panel provide a visual indication of the
auto null process, ashing orange when the auto null
process is active. Virtual LEDs in the STcontroller ap-
plication provide the same function. They are labeled
Ch A (Pin 3) and Ch B (Pin 3) to directly indicate which
auto null function is active.
If the auto null button is pressed, either on the front
panel or in STcontroller, when the associated Active
status LED is not lit the auto null process will not start.
The auto null LED will quickly ash orange four times
to indicate this condition.
Normally, the nulling process is performed at the time
of initial Model 545DC conguration but there’s no
reason why it can’t be initiated any time one desires.
The only time that auto null must be performed is
if conditions have changed with the party-line user
devices and wiring connected to a Model 545DC’s
party-line connector. Even a small change to a
party-line intercom circuit, such as adding or removing
a section of cable, may be enough to warrant that
the auto null process be performed.
An auto null sequence begins with the muting of the
Dante receiver (input) and Dante transmitter (output)
audio signal paths. If the Model 545DC is providing
power on the party-line interface, this is followed by a
short disconnection (break) in the 28 volts DC that is
sent to pin 2. This will turn o󰀨 microphones on those
connected user devices that are compatible with the
Clear-Com “mic kill” protocol. The actual auto nulling
process is performed next. A series of tones will be
sent to the party-line interface. Other Model 545DC
circuitry, under rmware control, will rapidly perform
adjustments to achieve the best null possible. After the
adjustments have been made the results are stored
in the Model 545DC’s non-volatile memory. Once
the process is complete, the Dante receiver (input)
and Dante transmitter (output) audio paths are again
activated.
If possible, prior to performing an auto null it’s polite
to warn all personnel who are actively using the con-
nected party-line intercom devices. The tones sent to
the party-line circuit during the nulling process are not
excessively loud or obnoxious, but most users might
want to remove their headsets during the process.
In addition to warning users, it might be a good time
to ask them to mute any active microphones. While
the automatic “mic kill” signal will be compatible with
many user devices it may not apply to all. Muting
microphones is signicant, as obtaining a “deep” null
requires that no extraneous signals be present on the
intercom circuit.