Studio Technologies 545DR User manual

50725-0522, Issue 1
Copyright © 2022 by Studio Technologies, Inc., all rights reserved
studio-tech.com
User Guide
Issue 1, May 2022
This User Guide is applicable for serial numbers
M545DR-00151 and later with Application Firmware 1.00 and later
and STcontroller application version 3.08.00 and later.
Model 545DR
Intercom Interface

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Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 3
Model 545DR
INTERCOM INTERFACE
Table of Contents
Revision History ................................................................................................................................ 4
Introduction........................................................................................................................................ 5
Getting Started .................................................................................................................................. 8
Dante Conguration .......................................................................................................................... 12
Model 545DR Conguration.............................................................................................................. 14
Operation........................................................................................................................................... 16
Technical Notes................................................................................................................................. 21
Specications .................................................................................................................................... 24
Appendix A–STcontroller Default Conguration Values..................................................................... 26
Appendix B– Graphical Description of the Installation Kit for Panel-Cutout or Surface-Mounting
Use (Order Code RMBK-10) ............................................................................................................. 27
Appendix C–Graphical Description of Left- or Right-Side Rack-Mount Installation Kit for
One “1/2- Rack” Unit (Order Code RMBK-11)................................................................................... 28
Appendix D–Graphical Description of Rack-Mount Installation Kit for Two “1/2- Rack” Units
(Order Code RMBK-12)..................................................................................................................... 29
Appendix E–Graphical Description of Center Rack-Mount Installation Kit for One “1/2- Rack”
Unit (Order Code RMBK-13) ............................................................................................................. 30

Issue 1, May 2022 Model 545DR User Guide
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Model 545DR
INTERCOM INTERFACE
Revision History
Issue 1, May 2022:
•Initial release.

Model 545DR User Guide Issue 1, May 2022
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Model 545DR
INTERCOM INTERFACE
Introduction
The Model 545DR Intercom Interface allows 2-
channel analog party-line (PL) intercom circuits
and user devices to be incorporated into Dante
®
audio-over-Ethernet applications. Analog party-line
intercom is commonly used in broadcast, corporate,
and commercial applications where a simple, reliable,
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 545DR directly supports both analog PL
and Dante, providing excellent performance in both
domains. The popular RTS
®
TW 2-channel analog
intercom circuit technology is directly compatible with
the Model 545DR. The Dante audio-over-Ethernet
media networking technology is used to transport
the two send and two receive audio channels asso-
ciated with this type of party-line circuit. The Model
545DR’s two hybrid circuits with automatic nulling
action provide good separation of send and receive
audio with high return loss and excellent audio qual-
ity. (These hybrid circuits are sometimes referred to
as 2-wire to 4-wire converters.) The Model 545DR’s
digital audio signals are compatible with all broadcast
and audio equipment that utilizes Dante technology.
An Ethernet connection is all that’s required to make
the Model 545DR part of a sophisticated, networked
audio system.
The Model 545DR can interconnect with Dante-
supported devices such as matrix intercom systems,
Figure 1. Model 545DR Intercom Interface front and back views
digital audio processors, and audio consoles. The
unit is directly compatible with the RTS ADAM
®
OMNEO
®
matrix intercom network. Alternately, two
Model 545DR units can be interconnected by way of
an associated Ethernet network. The Model 545DR
can also become part of a PL intercom system when
used in conjunction with devices such as the Models
5421 and 5422A Dante Intercom Audio Engine units
from Studio Technologies. In this way, an analog
party-line intercom circuit can become part of a high-
performance digital party-line intercom deployment.
The Model 545DR can be powered by Power-over-
Ethernet (PoE) or an external source of 12 volts
DC. The unit can provide a party-line power source
and impedance termination networks to allow direct
connection of 2-channel user beltpacks. This ability
allows support for connection of up to three of the
popular RTS BP-325 beltpacks. A Model 545DR can
also connect with an existing powered and terminat-
ed PL intercom circuit. The unit provides four audio
level meters that help to conrm system performance
during setup and operation. Support for transporting
call light signals between two Model 545DR units, as
well as between a Model 545DR and other compatible
units, is also provided.
The STcontroller software application can be used to
real-time monitor and control several Model 545DR
operating parameters. In addition, two conguration
settings are performed using the application. Versions
of STcontroller are available that are compatible with
PHOTO COMING SOON

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Page 6 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
the Windows
®
and macOS
®
operating systems. They
are available, free of charge, from the Studio Tech-
nologies’ website.
Standard connectors are used for Model 545DR
party-line (PL) intercom, Ethernet, and DC power in-
terconnections. Set up and conguration of the Model
545DR 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 545DR units to be mounted in one
space (1U) of a standard 19-inch rack enclosure.
Applications
There are three main ways that the Model 545DR
can be used in applications: connecting analog
party-line (PL) intercom circuits to Dante-based
intercom applications, adding party-line (PL) inter-
com support for matrix intercom systems, and linking
two stand-alone analog party-line intercom circuits.
The Model 545DR’s Dante transmitter (output)
and receiver (input) channels can be connected to
Dante-based digital PL intercom circuits. These cir-
cuits would typically be created using devices such
as the Studio Technologies’ Models 5421 or 5422A
Dante Intercom Audio Engines. This would allow
legacy analog equipment to become part of contem-
porary all-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 with OMNEO, can be routed
to the Model 545DR’s Dante transmitter (output) and
receiver (input) channels. The Model 545DR’s cir-
cuitry will then convert these signals into a 2-channel
analog party-line intercom circuit. In this way, adding
analog party-line support to RTS + OMNEO is a
simple task. The Model 545DR can also be used with
matrix intercom systems that don’t support Dante. An
external analog-to-Dante interface can be used to
convert analog intercom ports to Dante channels. For
example, the Model 544D Audio Interface from Studio
Technologies is specically designed to work with
matrix intercom systems. Once in the Dante digital
domain, these channels can be interconnected with
the Model 545DR’s Dante input and output channels.
Two separate analog party-line (PL) intercom circuits
can easily be interconnected using two Model 545DR
Interfaces. A Model 545DR is connected to each PL
circuit as well as to the Dante network. The Dante
Controller software application will then be used to
route (subscribe) the audio channels between the two
units. (The physical distance between units will only
be limited by the deployment of the LAN’s subnet.)
That’s it — nothing else is required to achieve excel-
lent performance.
The Model 545DR can also be used to “bridge” a
2-channel party-line intercom circuit with one or
two single-channel party-line intercom circuits. This
involves using a Model 545DR with the 2-channel
circuit and one or two of the Studio Technologies’
Model 545DC Intercom Interface units that support
single-channel party-line intercom circuits. The Model
545DC is a “cousin” of the Model 545DR and supports
two single-channel party-line intercom circuits rather
than one 2-channel circuit. These single-channel
circuits, typically supported by equipment from Clear-
Com
®
, are commonly used in theatrical and entertain-
ment applications.
Party-Line Interface
As previously discussed, the Model 545DR’s
party-line intercom interface is optimized for con-
nection with 2-channel party-line intercom circuits
and user devices such as the TW-series from RTS.
In addition, other industry-standard single- and
2-channel party-line intercom circuits and user devic-
es, including those from Clear-Com, are compatible.
(While the Model 545DR will function in a limited
manner with single-channel Clear-Com circuits, the
Model 545DC Intercom Interface unit is a much-
preferred choice for that.) A party-line active detection
function ensures that should a user beltpack or active
party-line intercom circuit not be connected the Model
545DR’s interface circuitry will remain stable. This
unique feature makes certain that objectionable audio
signals, including oscillations and “squeals,” won’t be
sent to other Dante-enabled devices.
A significant capability of the Model 545DR’s
party-line interface is its ability to supply DC power
and 200 ohms AC terminations to “create” an inter-
com circuit. The 29 volt output can power a moderate

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Model 545DR
INTERCOM INTERFACE
number of devices such as beltpacks. With up to
240 milliamperes (mA) of current available, a typical
broadcast application which uses up to three BP-325
beltpacks can be supported. 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 output is
monitored for over-current and short-circuit conditions.
Under rmware (embedded software) control the out-
put 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 545DR
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
assigned to the Model 545DR using the Dante Con-
troller application. This makes it simple to select
the way in which a Model 545DR ts into a specic
application.
Analog Hybrids with Auto Nulling
Circuits referred to as “hybrids” interface the Dante
transmitter (output) and receiver (input) channels with
the two channels of the party-line circuit. 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 545DR’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 545DR’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
connected party-line cabling and user devices.
Whenever the Model 545DR’s auto null button is
pressed, or the STcontroller application is used, digital
circuitry adjusts the hybrids to achieve their maximum
return-loss in less than 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 545DR’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 substan-
tial “nulls.” Moreover, the Model 545DR’s party-line
intercom power source o󰀨ers a unique level of perfor-
mance; its ability to deliver power while maintaining
audio quality is simply unmatched.
Audio Meters
The Model 545DR 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 channel. 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 545DR unit.
Status Display
LED indicators are provided on the Model 545DR’s
front panel, o󰀨ering a status indication of the party-line
(PL) power source, party-line (PL) activity status, and
the two auto null functions. Two other LEDs o󰀨er a
direct indication of what power source or sources
are connected to the Model 545DR. The STcontroller
application provides a real-time “virtual” status display
of the unit’s PL power source, PL activity, and auto
null functions.
Call Light Support
RTS TW-compatible party-line intercom user devices,
such as the BP-325 beltpack, provide a call light func-
tion using a 20 kHz square-wave signal that is added
to the designated audio path. To achieve optimal
audio performance this signal, along with essentially
all content above 10 kHz, is normally removed from
the audio signal that is sent out the Model 545DR’s
Dante transmitter (output) channels. It’s also removed

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INTERCOM INTERFACE
from the audio signal that arrives by way of the Model
545DR’s Dante receiver (input) channels. While the
result is excellent party-line talk audio, 20 kHz call light
signals are prevented from being directly sent to and
received from multiple Model 545DR units. A Model
545DR feature overcomes this limitation, detecting
the call light activity and re-generating it (again as a
20 kHz tone) in the applicable audio path. This allows
reliable “end-to-end” call light support between two
Model 545DR units. It also allows a Model 545DR to
send and receive call light status signals with an in-
terconnected Model 45DC or Model 545DC Intercom
Interface. These units are typically used with Clear-
Com party-line user beltpacks including the popular
RS-501 and RS-701.
Ethernet Data, PoE, and DC Power
Source
The Model 545DR 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
545DR’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 545DR’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 con-
nected simultaneously. An internal switch-mode
power supply ensures that all Model 545DR features,
including party-line intercom circuit power, are avail-
able 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 545DR 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 can be made using 3-pin male and
female XLR connectors. The Model 545DR 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 545DR units to be mounted in one space
(1U) of a standard 19-inch rack enclosure.
Future Capabilities and Firmware
Updating
The Model 545DR was designed so that its capa-
bilities and performance can easily be enhanced in
the future. A USB receptacle, located on the Model
545DR’s back panel, allows the application rmware
(embedded software) to be updated using a USB
ash drive. To implement its Dante interface the Model
545DR 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 545DR. 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 connec-
tors. Connections to an existing party-line intercom
circuit or one or more party-line user devices will be
made using one of 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 545DR
Intercom Interface and instructions on how to obtain
an electronic copy of this guide. An optional instal-
lation kit allows a Model 545DR to be mounted in a
rectangular opening in a tabletop or attached to a at
surface. If one or two Model 545DR units are going to
be mounted in a 19-inch equipment rack then having
another of the optional rack-mount installation kits is

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Studio Technologies, Inc. Page 9
Model 545DR
INTERCOM INTERFACE
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
source is included. (A compatible power supply, the
Studio Technologies’ PS-DC-02, is available as an
option.)
Locating the Model 545DR
Where to locate a Model 545DR will depend on be-
ing able to access the associated party-line circuit 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 545DR 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 545DR’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 545DR’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 545DR Unit
Installation kit RMBK-10 allows one Model 545DR 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 545DR’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 545DR’s enclo-
sure. Orient the standard-length bracket such that its
front is parallel to the Model 545DR’s front panel. The
screws will mate with the threaded fasteners that can
be seen on the side of the Model 545DR’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 545DR’s
enclosure.
Once the two standard-length brackets have been
installed the Model 545DR 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 545DR 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 545DR’s enclosure. The
screws will mate with the threaded fasteners that can
be seen on the side of the Model 545DR’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 545DR’s enclosure.
Once the two standard-length brackets have been
installed the Model 545DR 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 545DR Unit
Installation kit RMBK-11 allows one Model 545DR
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

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Model 545DR
INTERCOM INTERFACE
bracket, and four 6-32 thread-pitch Phillips-head
machine screws. Refer to Appendix C 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 the Model 545DR’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 545DR’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
545DR’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 545DR’s
enclosure.
Once the standard-length and long-length brackets
have been installed the Model 545DR 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 545DR Units
Installation kit RMBK-12 is used to allow two Model
545DR 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 545DR and one other
Studio Technologies’ product that is compatible with
the RMBK-12, such as the Model 5421 Dante Inter-
com Audio Engine. The RMBK-12 installation kit con-
tains 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 545DR
units. The screws will mate with the threaded fasten-
ers that can be seen on the side of the Model 545DR’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 545DR
unit.
Again using two of the 6-32 machine screws, attach
the second standard-length bracket onto the right side
of the second Model 545DR 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 545DR 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 545DR
Unit
Installation kit RMBK-13 allows one Model 545DR
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.

Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 11
Model 545DR
INTERCOM INTERFACE
Get ready to install the kit by removing the four ma-
chine screws and associated “bump on” protectors
from the bottom of the Model 545DR’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 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 545DR’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 545DR’s enclosure.
Once the two medium-length brackets have been in-
stalled the Model 545DR 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
545DR 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
545DR. To support a PoE Ethernet switch (PSE) that
includes power management capability the Model
545DR 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 545DR. 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 545DR’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 545DR by way of a 4-pin male XLR
connector which is located on the back panel. While
the stated requirement for the external source is nom-
inally 12 volts DC, correct operation will take place
over a 10 to 18 volts DC range. The Model 545DR
requires a maximum current of 1.0 amperes for cor-
rect operation. The DC source should be terminated
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 Technologies, is
directly compatible. Its AC mains input allows connec-
tion 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) can serve as the
Model 545DR’s power source. Alternately, an external
12 volts DC source can be connected. For redundan-
cy, 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 pro-
vide the Model 545DR’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 545DR’s party-line intercom interface
is designed to function in two distinct ways. It can
be connected to a “powered” broadcast-standard
2-channel party-line intercom circuit. Alternately, it
can be connected directly to party-line intercom user
devices. A 2-channel party-line intercom circuit, such
as one associated with TW-series equipment from
RTS, will have DC power and two audio channels on
a 3-pin XLR connector. These connectors will be wired
such that common is on pin 1 and 28 to 32 volts DC is
on pin 2. Channel 1 audio is superimposed on the DC
present on pin 2 while channel 2 audio is present on
pin 3. The party-line intercom circuit will also include
two impedance-generating networks that provide 200
ohms audio (AC) loads from pin 2 to pin 1 and from
pin 3 to pin 1. When the Model 545DR’s party-line
interface is connected to an existing intercom circuit
it will act, from an audio standpoint, as a standard
party-line intercom user device. It won’t draw (nor
supply) any DC power.

Issue 1, May 2022 Model 545DR User Guide
Page 12 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
The Model 545DR’s party-line interface can also serve
to create a “mini” 2-channel intercom circuit. It can
provide a 29 volts DC, 240 milliamperes maximum,
power source along with two 200 ohms impedance
generators. This relatively modest amount of current
will allow a limited number of 2-channel intercom user
devices to be directly connected. Many broadcast ap-
plications use the popular RTS BP-325 user beltpack
and the Model 545DR’s intercom interface can directly
support up to three of them. Wiring from the Model
545DR’s intercom interface to one or more of the
BP-325 devices requires that a 1-to-1, 2-to-2, 3-to-3
wiring scheme on associated 3-pin XLR connectors
be maintained.
For convenience, the party-line intercom circuit and/or
user devices can connect to the Model 545DR by way
of the male and female 3-pin XLR connectors that are
located on the unit’s back panel. The two connectors
are wired in parallel (“multed”) and provide access to
the identical signals.
Compatibility with Single-Channel
Intercom Systems
As previously discussed, the Model 545DR is
designed to directly support 2-channel party-line
intercom circuits and user devices. Applications that
involve single-channel party-line intercom circuits and
user devices (typically associated with products from
Clear-Com) can also be supported. These circuits and
devices typically utilize common on pin 1, power on
pin 2, and audio on pin 3. When this kind of intercom
circuit is directly connected to the Model 545DR’s
intercom interface only channel 2 will be active; chan-
nel 1 would not be utilized.
A better means to support these single-channel
party-line intercom circuits and user devices is to
use the Studio Technologies’ Model 45DC or Model
545DC Intercom Interface units. They are “cousins”
of the Model 545DR and optimized for single-channel
party-line intercom applications. Rather than provid-
ing a single 2-channel interface, these units provide
two single-channel-optimized party-line intercom
interfaces. Detailed information about the units will
be available on the Studio Technologies’ website
(studio-tech.com).
Dante Conguration
To integrate the Model 545DR into an application
requires that a number of Dante-related parameters
be configured. These configuration settings will
be stored in non-volatile memory within the Model
545DR’s Dante interface circuitry. Conguration will
typically be done using the Dante Controller software
application 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 545DR
uses the UltimoX2 2-input/2-output integrated circuit
to implement its Dante interface. The Model 545DR’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 545DR’s two Dante receiver (input) channels.
The Model 545DR’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 Mod-
el 545DR’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 545DR’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 545DR 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 545DR 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 545DR units will

Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 13
Model 545DR
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 1
channel on each unit would be routed (subscribed) to
the To Party-Line Channel 1 channel on the other unit.
And the From Party-Line Channel 2 channel on each
unit would be routed (subscribed) to the To Party-Line
Channel 2 channel on the other unit.
The other typical application will have one Model
545DR connected to an existing party-line inter-
com circuit or a set of user devices. Then the unit’s
Dante 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 545DR 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 545DR.
Device and Channel Names
The Model 545DR has a default Dante device name
of ST-545DR- followed by a unique su󰀩x. (A technical
reason prevents the default name to be the preferred
ST-M545DR- (an “M” included). But that can be added
by the user.) The su󰀩x identies the specic Model
545DR 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 PL Ch1 and From PL Ch2.
The unit’s two Dante receiver (input) channels have
default names of To PL Ch1 and To PL Ch2. Using
Dante Controller, the default device and channel
names can be revised as appropriate for the specic
application.
Device Conguration
The Model 545DR 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 545DR’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 545DR’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 545DR can be congured for AES67 op-
eration. 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 545DR Clocking Source
While technically the Model 545DR 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 545DR would not want to
be enabled.

Issue 1, May 2022 Model 545DR User Guide
Page 14 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
Model 545DR Conguration
The STcontroller software application is used to congure two Model 545DR functions, call light support and
PL active detection. (STcontroller also allows real-time display and control of other Model 545DR 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 545DR
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 545DR 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 545DR 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
545DR 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 545DR’s front panel will ash in a distinctive pattern.
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 545DR’s current detection function 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 the PL interface for the Model
545DR to recognize a “PL active” condition. When
this minimum current condition is met the LED labeled

Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 15
Model 545DR
INTERCOM INTERFACE
ACTIVE on the unit’s front panel will light green, the
PL Active status icon on the STcontroller’s menu
page will show green, and the two Dante transmitter
(output) audio paths will be active. Having the PL
Active Detection function enabled is appropriate for
most applications, helping to maintain the most stable
audio performance. Only when su󰀩cient current is
drawn from pin 2 of the Model 545DR’s PL interface
will audio from the PL channels be sent out the Dante
transmitter (output) channels.
When the PL Active Detection configuration is
selected to O (disabled), no minimum current draw
is required on pin 2 of the PL interface for the ACTIVE
LED to be lit, the STcontroller graphics icon to display
green, and the two Dante transmitter (output) chan-
nels 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 545DR is being used with a Telex
®
BTR-800
Wireless Intercom System. The BTR-800 is designed
to directly interface with a party-line (PL) intercom
circuit. This circuit would typically have DC power and
one or two audio channels associated with it. (Each
audio channel would typically have a terminating
impedance of nominally 200 ohms.) The Model
545DR can provide such a PL circuit when the local
power source is enabled. But a problem arises as
the BTR-800 does not draw current from pin 2 of the
connected PL intercom circuit. It doesn’t function in
the same manner as would a typical PL intercom
beltpack or user device. The BTR-800 doesn’t use
power from the PL connection, instead using its in-
ternal power source for operation. In this case, the
Model 545DR’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 two
Dante transmitter (output) audio paths would not be
enabled. Users of the BTR-800 would receive Model
545DR Dante receiver (input) audio but would not
send audio out the two Dante transmitter (output)
channels. Turning o󰀨 the PL Active Detection function
would resolve this issue. Even though no DC current
would be supplied by the Model 545DR’s PL interface,
the Dante transmitter (output) channels would be
enabled and successful PL interface operation could
take place.
When the Model 545DR 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 ap-
proximately 18 or greater is present on pin 2 of the
PL interface will the Model 545DR recognize that a
valid PL interconnection has been made. In this case,
the ACTIVE LED on the front panel will light green,
the virtual button in STcontroller will light green, and
the Dante transmitter (output) audio channels will
be active. When the PL Active Detection function is
disabled, monitoring of DC voltage on pin 2 of the
Model 545DR’s PL interface will not take place. In
this situation, the ACTIVE LED on the Model 545DR’s
front panel will always be lit, the virtual indicator 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, May 2022 Model 545DR User Guide
Page 16 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
Operation
At this point, the Model 545DR should be ready for
use. The party-line intercom and Ethernet connections
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 includ-
ed with the Model 545DR. One can be purchased as an
option.) The Dante receiver (input) and transmitter (out-
put) channels should have been routed (subscribed)
using the Dante Controller software application. Normal
operation of the Model 545DR can now begin.
On the front panel, multiple LEDs provide an indication
of the unit’s operating status. In addition, a pushbutton
switch is provided to select the on/o󰀨 status of the local
power function as well as activating the auto null func-
tion. 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 control of the on/o󰀨 status
of the local power source in addition to initiating the
auto null function.
Initial Operation
The Model 545DR will begin its initial functioning
a few seconds after its power source is connected.
As previously discussed, the power source 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 545DR 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 associated
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 start indicating the operating status
of the Dante interface, turning green as valid conditions
are established. The Ethernet LINK/ACT, also located
on the back panel, will start 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 545DR 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 configuration of the unit’s
Dante interface. Details will be covered in the next
paragraph. On the front panel, the user is presented
with one pushbutton switch, two input power status
LEDs, two party-line intercom circuit status LEDs, two
auto null LEDs, and four 5-segment LED level meters.
These resources are simple to understand and con-
trol, 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 545DR’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 op-
erating status of the Dante interface and associated
network. The SYS LED will light red upon Model
545DR 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 545DR is not synchronized with a Dante net-
work. It will light solid green when the Model 545DR
is synchronized with a Dante network and an external
clock source (timing reference) is being received.
It will slowly flash green when this specific Model
545DR unit is part of a Dante network and is serving
as a Leader clock. (It’s important to note that typical
applications will not have a Model 545DR unit serving
as a Dante Leader clock.)
How to Identify a Specic
Model 545DR
Both the Dante Controller and STcontroller software
applications offer identify commands that can be
used to help locate a specic Model 545DR. When
an identify command is selected for a specic Model
545DR 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
545DR level meter and Dante status LED operation
will again take place.

Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 17
Model 545DR
INTERCOM INTERFACE
Level Meters
The Model 545DR 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 channels.
General
The meters are organized into two groups with each
group representing one channel of audio being sent
to the party-line circuit and one channel of audio
being returned by the party-line circuit. The meters
are calibrated to reect the level in dB relative to the
reference (nominal) level of the party-line intercom
circuit. The Model 545DR’s nominal party-line level
was selected to be –10 dBu, matching that utilized by
typical 2-channel party-line intercom circuits.
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
–10 dBu. The top LED is yellow and indicates a sig-
nal that is 6 dB or greater than the –10 dBu nominal
level. An audio signal that causes the yellow LED to
light doesn’t necessarily indicate an excessive level
condition, but it does provide a warning that reducing
the signal level may be prudent. Typical operation
with normal signal levels should find the meters
lighting near their 0 point. Signal peaks may cause
the yellow LEDs to ash. A yellow LED that lights fully
during normal operation will indicate an excessive
signal level conguration and/or a conguration prob-
lem with associated Dante-enabled equipment.
As an example of how the meters function, let’s review
the situation where the CHANNEL 1 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 –10 dBu
is being sent to channel 1 of the party-line intercom
circuit. This would be a very appropriate signal level
and should provide excellent operation. Also note
that this –10 dBu signal being that is being sent to
the party-line intercom channel would translate into a
–20 dBFS digital audio signal present on the associ-
ated receiver (input) channel of the Dante interface.
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
equipment connected to the associated Dante receiv-
er (input) and/or Dante transmitter (output) channels.
(It would be almost impossible for this situation to
occur if two Model 545DR 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) port such that it results in nominal
audio levels of –20 dBFS on the associated Dante
transmitter (output) and receiver (input) channels. Pro-
viding compatible digital audio reference levels would
lead to the best performance of the Model 545DR 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 545DR’s party-line intercom circuit. These ana-
log signals are converted to digital and then output on
Dante transmitter (output) channels. For a party-line
intercom circuit 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 one or two intercom termination networks.)
An issue may arise if the audio signals coming from
the connected party-line intercom circuit or user
devices aren’t at a su󰀩cient level such that normal
meter display levels can be reached. It’s possible that

Issue 1, May 2022 Model 545DR User Guide
Page 18 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
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 approximately 100 ohms (two sources, each 200
ohms, connected in parallel) which would cause major
issues. The most evident problem would be that the
intercom channel’s nominal audio levels would attenu-
ate (drop) by about 6 dB. In addition, auto null circuits,
such as provided by the Model 545DR, will not be
able to obtain good separation (nulling) performance.
Removing the unwanted second termination (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. It’s easily possible for the Model
545DR’s local power source, which provides both
DC power and 200 ohms termination networks for
the two channels, to be accidentally enabled when
the Model 545DR is connected to an externally pow-
ered and terminated party-line circuit. This would be
incorrect, leading to the “double-termination” con-
dition. Turning off the Model 545DR’s local power
source by pressing and holding the 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 application. 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
channels.
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 whenev-
er 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 545DR’s
operating power.
Party-Line Operating Mode
Selection
As discussed previously, the Model 545DR provides
two party-line circuit operating modes. One mode is
used when the Model 545DR is required to create
a 2-channel party-line intercom circuit, providing
29 volts DC and two 200 ohms termination imped-
ance networks. In this mode, user devices such as
beltpacks can be directly supported. The 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 545DR to be
connected to a 2-channel party-line intercom circuit
that provides both DC power and two channels of 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 to the desired operating mode is simple,
only requiring the AUTO NULL pushbutton switch to
be pressed and held for a minimum of two seconds.
This will cause the Model 545DR’s operating mode
to change (“toggle”) from one mode to the other. As
the mode changes, the LOCAL POWER status LED
and STcontroller application will display accordingly.
Once the mode has changed the pushbutton switch
can then be released. The operating mode can also
be selected using the virtual pushbutton switch in
the STcontroller software application. The selected
operating mode will be stored in non-volatile mem-
ory, ensuring that it will restore to that value after a
power-down/power-up cycle.
Local Power Mode Operation
When the Model 545DR’s local power mode is
enabled, the unit will provide DC power and two 200
ohms termination impedances to create a 2-channel
party-line intercom circuit. The party-line interface
supplies 29 volts DC on pin 2 of the 3-pin XLR con-
nectors with a maximum current draw of 240 mA
available. This current is su󰀩cient to power various
intercom user devices such as small user stations and
beltpacks. A common broadcast application may use
RTS BP-325 beltpacks. Select the connected devices
so that their total maximum current doesn’t exceed

Model 545DR User Guide Issue 1, May 2022
Studio Technologies, Inc. Page 19
Model 545DR
INTERCOM INTERFACE
240 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 original (very, very early) version of the
BP-325 consumes a maximum of 85 mA of current.
According to this gure, one or two of these units can
be connected to a Model 545DR. All newer versions of
the BP-325 use surface-mount component technology
and have a maximum current draw of 65 mA. Up to
three of these “modern” BP-325 units can easily be
supported.
When local power has been enabled, the ACTIVE
status LED will light green when a minimal amount
of current is flowing from the Model 545DR to the
connected user device or devices. This will also cause
the 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 545DR’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 two Dante
transmitter (output) audio channels to be in their
active (unmuted) state. (By muting the Dante trans-
mitter (output) channels when the intercom circuit is
not active, unwanted audio signals will be prevented
from passing to the outside world when no party-line
devices are 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 the party-line XLR
connectors is required for the ACTIVE status LED
to light, the virtual LED in the STcontroller applica-
tion to light green, and the two transmitter (output)
audio paths to be active. This function is called
PL Active Detection and disabling it can be appro-
priate for special applications. Refer to the Model
545DR Conguration section for details regarding this
function and how it may be utilized.
The Model 545DR’s party-line intercom power supply
circuit operates under rmware control. This allows
detection of fault conditions and protection of the unit’s
circuitry. Upon initially enabling the Model 545DR’s
party-line intercom power supply no monitoring of
the intercom power output takes place for three sec-
onds. This allows the Model 545DR’s intercom power
supply circuitry and the connected intercom user
device or devices to stabilize. The 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 connectors, will light to indicate
that the output is active. The PL Active virtual LED
in STcontroller will light green. After this initial de-
lay, 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 momentarily turning o󰀨 the DC
power source to pin 2. It will also, as a warning, ash
the 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 the Model 545DR’s party-line 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 the LOCAL POWER status LED on the front
panel is not lit, and the virtual pushbutton switch in
STcontroller is labeled Off, the Model 545DR’s
party-line interface does not provide DC power on
pin 2 of the XLRs nor provides 200 ohms terminating
impedances on pins 2 and 3. In this mode, the Model
545DR is intended to be connected to an externally
powered party-line circuit. This party-line circuit must
provide the DC power and termination impedances
required to create the party-line intercom circuit. In this
mode, the Model 545DR simply serves in the same
fashion as that of another connected user device. (In
e󰀨ect, the Model 545DR would have the technical
characteristics of a non-powered user device.) When
connected to a powered party-line circuit the Model
545DR’s ACTIVE status LED will light when approx-
imately 18 volts DC or greater is present on pin 2 of
the XLR connectors. In addition, the STcontroller’s PL
Active virtual LED will light green. When this condition
is detected, the Dante transmitter (output) channels
are placed in their active (non-muted) state. Other-
wise, they are o󰀨 (muted) to maintain stable Model
545DR performance.

Issue 1, May 2022 Model 545DR User Guide
Page 20 Studio Technologies, Inc.
Model 545DR
INTERCOM INTERFACE
As previously described, a setting in the STcotnroller
application can disable the requirement that 18 volts
DC or greater be present on pin 2 of the party-line XLR
connectors for the ACTIVE status LED to light, the PL
Active virtual LED to light green, and the transmitter
(output) audio paths 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 545DR Conguration section for details
regarding this function and how it may be utilized.
Auto Null
The Model 545DR contains circuitry to automatically
null the hybrid networks associated with the two
party-line interface channels. This procedure sep-
arates the audio signals as they are sent to and
received from the two channels associated with the
party-line intercom circuit. A pushbutton switch, locat-
ed on the front panel, is provided to activate the two
auto null functions, one for each channel. A virtual
(“soft”) button in the STcontroller software application
also allows 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 provide an indication of the operation
of the auto null circuits.
To initiate auto null first requires that the ACTIVE
status LED be lit. When the operating 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. Alternately, 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
is performed on both channels at essentially the same
time and take approximately 15 seconds to complete.
Two LEDs on the unit’s front panel provide a visual
indication of the auto null process, ashing orange
when the auto null process for its respective channel
is active. Virtual LEDs in the STcontroller application
provide the same function. They are labeled Ch 1
(Pin 2) and Ch 2 (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 ACTIVE status
LED is not lit the auto null process will not start. The
auto null LEDs will quickly ash orange four times to
indicate this condition.
Normally, the nulling process is performed at the time
of initial Model 545DR 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 545DR’s
party-line connectors. Even a small change to a
party-line intercom circuit, such as adding or removing
a section of cable, may be enough to require 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. This is followed by a short peri-
od of a 24 kHz sine wave signal that is sent to both
channels of the party-line intercom interface. This
will turn o󰀨 microphones on those connected user
devices that are compatible with the RTS TW-series
“mic kill” protocol. The actual auto nulling process is
performed next. A series of tones will be sent to both
channels of the party-line interface. Other Model
545DR 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 545DR’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.