Studio Technologies 370A User manual

50636-0623, Issue 4
Copyright © 2023 by Studio Technologies, Inc., all rights reserved
studio-tech.com
User Guide
Issue 4, June 2023
This User Guide is applicable for serial numbers
M370A-04501 and later with application rmware 2.1 and later
Model 370A
Intercom Beltpack

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Model 370A User Guide Issue 4. June 2023
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Model 370A
INTERCOM BELTPACK
Table of Contents
Revision History............................................................................................. 4
Introduction.................................................................................................... 5
Getting Started............................................................................................... 7
Dante Conguration....................................................................................... 8
Model 370A Conguration ............................................................................. 8
Operation...................................................................................................... 12
Technical Notes ............................................................................................ 15
Specications................................................................................................ 19
Appendix A: STcontroller Default Conguration Values ................................ 20

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INTERCOM BELTPACK
Revision History
Issue 4, June 2023:
• Adds screen capture for the STcontroller application.
• Miscellaneous improvements and clarications.
• Updated to meet latest document format.
Issue 3, May 2021:
• Documents changes to several specications.
Issue 2, August 2019:
• Documents revision to STcontroller (version 2.02.00 and later) which separates microphone power and microphone
gain conguration.
Issue 1, June 2018:
• Initial release.

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Model 370A
INTERCOM BELTPACK
Introduction
The Model 370A Intercom Beltpack begins with the
features o󰀨ered by traditional 2-channel party-line
intercom user devices and adds a range of new
capabilities, along with the advanced performance
and exibility that Dante
®
audio-over-Ethernet pro-
vides. Over a standard IP network, multiple Model
370A units can be used in party-line (PL) intercom
applications with help from an external Dante-enabled
audio matrix such as the Studio Technologies’ Model
5422A Dante Intercom Audio Engine. Alternately, units
can be used “point-to-point” or interfaced with Dante-
compatible matrix intercom systems.
Only a single Power-over-Ethernet (PoE) connection
is required for operation. Key user features can be
easily configured using the STcontroller software
application. Congurable parameters include electret
microphone powering, microphone preamplier gain,
talk button operation, and headphone channel as-
signment. User features include integrated sidetone,
call function, and remote mic kill (“talk o󰀨”). The wide
range of capabilities, along with the excellent audio
quality provided by the digital audio signal path, o󰀨ers
a unique and powerful user experience.
Set up and conguration of the Model 370A is simple.
An etherCON
®
RJ45 jack is used to interconnect with
a standard twisted-pair Ethernet port associated with
a local-area network (LAN). This connection provides
both power and bidirectional digital audio. A broadcast
or intercom-style stereo or monaural headset with a
dynamic or electret (DC-powered) microphone inter-
faces with the unit using a 5-pin XLR connector.
The STcontroller software application is used to select
the unit’s operating parameters. Two talk pushbutton
switches can be congured for optimal operation. Two
push-in/push-out (“pop out”) rotary controls make
it easy to set and maintain the desired headphone
output level. The Model 370A’s enclosure is made
from an aluminum alloy which o󰀨ers both light weight
and ruggedness. A stainless steel “belt clip,” located
on the back of the unit, allows direct attachment to a
user’s clothing.
The audio quality of the Model 370A’s audio channels
is excellent, with low distortion, low noise, and high
headroom. Careful circuit design and rugged compo-
nents ensure long, reliable operation. A wide range of
applications can be supported, including sports and
entertainment TV and radio events, streaming broad-
casts, corporate and government AV installations, and
post-production facilities.
Dante Audio-over-Ethernet
Audio data is sent to and received from the Model
370A using the Dante audio-over-Ethernet media
networking technology. As a Dante-compliant device,
the Model 370A’s two Dante audio transmitter (output)
and two Dante audio receiver (input) channels can
be interconnected (routed) with other devices using
the Dante Controller software application. The Dante
transmitter (output) and receiver (input) channels are
limited to supporting four Dante ows, two in each
direction. The digital audio’s bit depth is up to 24 with
a sampling rate of 48 kHz. The Model 370A is AES67
compatible and compliant with the Dante Domain
Manager™ software application.
Two bi-color LEDs provide an indication of the Dante
connection status. The Dante Controller’s Identify
command takes on a unique role with the Model 370A.
Not only will it cause the talk and call button LEDs to
light in a unique highly visible sequence, it can also
be congured to turn o󰀨 any active talk channels.
Audio Quality
Figure 1. Model 370A Intercom Beltpack top and bottom views

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INTERCOM BELTPACK
The Model 370A’s completely “pro” performance is
counter to the less-than-stellar reputation of typical
party-line (PL) intercom audio. A low-noise, wide
dynamic-range microphone preamplier and asso-
ciated voltage-controlled-amplier (VCA) dynamics
controller (compressor) ensures that microphone
audio quality is preserved while minimizing the chance
of signal overload. DC power to support electret
microphones can be enabled if necessary. The output
of the microphone preamp and compressor is routed
to an analog-to-digital converter (ADC) section that
supports a sampling rate of 48 kHz with a bit depth of
up to 24. The audio signal, now in the digital domain,
travels through the processor and on to the Dante
interface section where it is packetized and prepared
for transport over Ethernet.
Audio input signals arrive via two Dante receiver
(input) channels. The supported sampling rate is
48 kHz with a bit depth of up to 24. The audio signals
pass into the Model 370A’s processor where channel
routing, headphone level control, and sidetone cre-
ation are performed within the digital domain. This
provides flexibility, allowing precise control of the
audio signals and eliminating the need for the two
rotary level controls from having to directly handle
analog audio signals. The audio signals destined
for the 2-channel headphone output are sent to a
high-performance digital-to-analog converter and then
on to robust driver circuitry. High signal levels can be
provided to a variety of headsets, headphones, and
earpieces.
Call Function
A call function allows Model 370A users to send and
receive channel-specic visual alert signals. Pressing
the call pushbutton on the top of the unit is all that’s
required to signal other users that attention is request-
ed. Using 20 kHz tones, the call signals are sent within
the audio channels (“in band”) allowing interoperability
between multiple Model 370A units as well as being
compatible with legacy party-line intercom systems.
Call signals can be useful to indicate to users that
they are needed “on headset” or should be actively
listening to an intercom channel. The call function can
also be used to provide real-time cues to production
personnel during the running of live events.
Conguration Flexibility
A highlight of the Model 370A is its ability to be easily
congured to meet the needs of specic users and
applications. All conguration choices are made using
the STcontroller software application that commu-
nicates with the Model 370A by way of an Ethernet
network connection. Congurable parameters include
microphone power and preamplier gain, sidetone
audio operation, talk button operation, and headphone
monitoring.
The microphone input can be selected for compati-
bility with dynamic or elected (DC-powered) micro-
phones. The gain of the microphone preamplier can
be selected from among four choices. These allow
compatibility with the variety of microphones that are
part of broadcast and intercom headsets.
A unique Model 370A feature is the ability to individu-
ally congure the way in which the two talk pushbutton
switches function; four choices are available. For stan-
dard intercom beltpack operation it’s typical to select
Push to Talk, Latching, or Push to Talk/Tap to Latch.
For situations where only monitoring of an intercom
channel is desired a Disabled mode is available.
Two audio channels arrive via Dante and are des-
tined for the 2-channel headphone output. Each
input source can be independently routed to the left
headphone channel, right headphone channel, or
both the left and right headphone channels. This ex-
ibility allows a variety of listening environments to be
created, including stereo, single-channel monaural,
and dual-channel monaural.
Ethernet Data and PoE
The Model 370A connects to an Ethernet data net-
work using a standard 100 Mb/s twisted-pair Ether-
net interface. The physical interconnection is made
by way of a Neutrik
®
etherCON RJ45 jack. While
compatible with standard RJ45 plugs, etherCON
allows a ruggedized and locking interconnection
for harsh or high-reliability environments. An LED
displays the status of the network connection.
The Model 370A’s operating power is provided by
way of the Ethernet interface using the 802.3af
Power-over-Ethernet (PoE) standard. This allows
fast and e󰀩cient interconnection with the associated
data network. To support PoE power management,
the Model 370A’s PoE interface reports to the power

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Model 370A
INTERCOM BELTPACK
sourcing equipment (PSE) that it’s a class 1 (very low
power) device.
Future Capabilities and Firmware
Updating
The Model 370A was designed such that its capabili-
ties and performance can be enhanced in the future.
A USB receptacle, located on the unit’s main circuit
board (underneath the unit’s cover), allows the appli-
cation rmware (embedded software) to be updated
using a USB ash drive.
The Model 370A uses Audinate’s Ultimo™ integrated
circuit to implement the Dante interface. The rmware
in this integrated circuit can be updated via the Ether-
net connection, helping to ensure that its capabilities
remain up to date.
Getting Started
What’s Included
Included in the shipping carton are a Model 370A
Intercom Beltpack and instructions on how to obtain
an electronic copy of this guide. As a device that is
Power-over-Ethernet (PoE) powered, no external
power source is provided. In most applications an
Ethernet switch with the required PoE capability will
be utilized.
Connections
In this section, signal interconnections will be made
using the two connectors located on the bottom of the
Model 370A’s enclosure. An Ethernet data connection
with Power-over-Ethernet (PoE) capability will be
made using either a standard RJ45 patch cable or
an etherCON protected RJ45 plug. A dual-channel
or single-channel (dual- or single-ear) headset will
be connected using a cable-mounted 5-pin male XLR
connector.
Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that supports
Power-over-Ethernet (PoE) is required for Model
370A operation. This one connection will provide
both the Ethernet data interface and power for the
Model 370A’s circuitry. A 10BASE-T connection is
not su󰀩cient and a 1000BASE-T (GigE) connection
is not supported unless it can automatically “fall back”
to 100BASE-TX operation. The Model 370A supports
Ethernet switch power management, enumerating
itself as a PoE class 1 device. Any source that is
compliant with the IEEE
®
802.3af standard will func-
tion correctly. Should the selected Ethernet switch
port support Energy-E󰀩cient Ethernet (EEE) it must
be disabled to help ensure reliable Dante operation.
The Ethernet connection is made by way of a Neutrik
etherCON protected RJ45 jack that is located on the
bottom of the Model 370A’s enclosure. This allows
connection by way of a cable-mounted etherCON
connector or a standard RJ45 plug. The Model 370A’s
Ethernet interface supports auto MDI/MDI-X so that a
crossover cable will never be required.
Headset Connection
The Model 370A provides a 5-pin female XLR con-
nector that interfaces with the microphone and head-
phone connections of an intercom or broadcast-style
headset. Refer to Figure 2 for connection details. The
microphone input connections are compatible with
most unbalanced dynamic or electret (low-voltage
DC-powered) microphones. A balanced dynamic
microphone should, in most cases, also function cor-
rectly if its signal – (low) is connected to Model 370A’s
mic in –/shield connection. No support is provided for
microphones that require P12 or P48 phantom power.
To allow users of stereo (dual-earpiece or “double
mu󰀨”) headsets to hear a monaural version of the two
headphone output channels does not require special
wiring of the 5-pin male XLR mating connector. The
headset’s left headphone channel should always be
wired to pin 4 and the right headphone channel to pin
5. Conguration choices, discussed later in this guide,
can then be used to create the desired monaural
output. It’s important not to connect together (short)
pins 4 and 5 of the Model 370A’s headset connector
as damage to the Model 370A’s output circuitry could
result.
Figure 2. Headset connection pinout chart

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Monaural (single-earpiece or “single mu󰀨”) headsets
should be wired such that its headphone is wired only
to pin 4; pin 5 should be remain unused. Conguration
choices, discussed later in this guide, can be used to
create a monaural output.
It’s possible that some beyerdynamic headset intercon-
necting cable assemblies terminate the earpiece’s left
and right connections opposite from what the Model
370A and other broadcast equipment require. These
cables may terminate the left earpiece to pin 5 of the
XLR connector and the right earpiece to pin 4. If this
condition is present it will require reversing or “ipping”
the two wires in a headset’s 5-pin male XLR connector
such that the left earpiece connects to pin 4 and the
right earpiece to pin 5.
Dante Conguration
For audio to pass to and from the Model 370A requires
that several Dante-related parameters be congured.
These configuration settings will be stored in non-
volatile memory within the Model 370A’s circuitry.
Configuration will typically be done with the Dante
Controller software application which is available for
download free of charge at audinate.com. Versions of
Dante Controller are available to support Windows
®
and OS X
®
operating systems. The Model 370A uses
the Ultimo 2-input/2-output integrated circuit to imple-
ment the Dante architecture.
The two Dante transmitter (output) channels associ-
ated with the Model 370A’s Dante interface must be
assigned to the desired receiver (input) channels.
This achieves routing the Model 370A’s two talk
output audio channels to the device (or devices) that
will be “listening” to them. Within Dante Controller a
“subscription” is the term used for routing a transmitter
ow (a group of output channels) to a receiver ow (a
group of input channels). The number of transmitter
ows associated with an Ultimo integrated circuit is
limited to two. These can either be unicast, multicast,
or a combination of the two. If the Model 370A’s Dante
transmitter (output) channels need to be routed using
more than two ows it’s possible that an intermediary
device, such as the Studio Technologies’ Model 5422A
Dante Intercom Audio Engine, can be used to “repeat”
the signals. (Use the Model 5422A’s pass-thru group
conguration mode to provide this resource.)
The two Dante receiver (input) channels associated
with the Model 370A’s audio inputs also need to be
routed to the Dante transmitter (output) channels pro-
vided by the desired source device. These two audio
signals can be sent to the Model 370A’s 2-channel
headphone output.
The Model 370A supports an audio sample rate of
48 kHz with no pull-up/pull-down values available. The
Model 370A can serve as the Leader clock for a Dante
network but in most cases it will be congured to “sync”
to another device that is serving as the “grand Leader”
for the Dante implementation.
The Model 370A has a default Dante device name
of ST-M370A- followed by a unique su󰀩x. The su󰀩x
identies the specic Model 370A that is being cong-
ured. The su󰀩x’s actual alpha and/or numeric char-
acters relate to the MAC address of the unit’s Ultimo
integrated circuit. The two Dante transmitter (output)
channels have default names of Ch1 and Ch2. The two
Dante receiver (input) channels have default names of
Ch1 and Ch2. Using the Dante Controller application
the default device name and channel names can be
revised as appropriate for the specic application.
Model 370A Conguration
Many of the Model 370A’s operating parameters can
be congured to match the needs of specic applica-
tions. The STcontroller software application is used
to observe a unit’s current conguration and perform
any changes that are required. No DIP switch settings
or other local actions are used to congure the unit.
This makes it imperative that the STcontroller software
application be available for use in a personal computer
that’s connected to the related LAN.
STcontroller is available free of charge on the Studio
Technologies’ website (studio-tech.com/stcontroller)
and is compatible with personal computers running
Windows
®
and macOS
®
operating systems. If neces-
sary, download and install STcontroller onto a designat-
ed personal computer. This personal computer must be
on the same local area network (LAN) and subnet as
the Model 370A unit or units that are to be congured.
Changes made using STcontroller will be immedi-
ately reected in the unit’s operation; no Model 370A
“reboot” is required. Each time a change is made the
three buttons, talk 1, talk 2, and call, on the top panel
will momentarily ash orange in a distinctive pattern to
indicate that a command from STcontroller has been
received.

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Using STcontroller
Immediately after starting STcontroller the application will locate and display the devices that it can control.
The one or more Model 370A units that are recognized will appear in the device list. Use the Identify com-
mand to allow easy recognition of a specic Model 370A unit. Double clicking on a device name will cause the
associated conguration menu to appear. Review the current conguration and make changes as required.
Microphone Input – Electret Power
Choices are Enabled or Disabled.
If the headset has an electret microphone that re-
quires a source of low-voltage DC power for operation
enable the Electret Power check box. If the associated
headset has a dynamic (non-powered) microphone
do not enable the Electret Power check box. Most
broadcast headsets that terminate on a 5-pin male
XLR connector will not require microphone power.
The on/o󰀨 status is displayed by way of a red LED,
labeled MIC POWER, that is located adjacent to the
headset connector.
Note that the Model 370A cannot supply P12 or P48
phantom power that may be required for balanced
condenser (capacitor) microphones. This should not
pose an issue as this type of microphone is essentially
never associated with a headset that would be used
for intercom applications.
Microphone Input – Gain
Choices are 22 dB, 30 dB, 42 dB, and 48 dB.
Dynamic microphones have an output level that is
typically lower than that provided by electret micro-
phones. As such, the 42 or 48 dB gain settings will
probably be appropriate for them. Electret micro-
phones often have internal circuitry which provides
a relatively high output level. The 22 and 30 dB gain
settings will typically be appropriate with this type of
microphone.
When a dynamic microphone is connected to the
Model 370A the 42 dB gain setting may be correct for
many applications. Setting the gain for 48 dB may be
helpful in some applications, such as with headsets
that have a low microphone output level. The 48 dB
gain setting may also be useful when the Model 370A
is going to be deployed at events where users are not

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able to speak at normal levels, e.g., sporting events
such as golf tournaments where “whispering” may
be necessary.
Electret microphones typically have a higher out-
put level due to their internal preamplier circuitry.
As such, less preamplifier gain may be required.
Selecting the 22 or 30 dB gain setting will probably
be appropriate in these cases.
The compressor active LED, labeled COMP and vis-
ible adjacent to the headset connector, can act as a
guide when setting the microphone preamplier gain.
During normal talk operation the compressor active
LED should light intermittently. If, for example, with
a dynamic microphone the LED rarely lights and the
preamp gain is set to 42 dB it might be a good idea to
change it to 48 dB. If the LED is lit fully during normal
talking in a situation where the headset has an electret
microphone and the gain is set for 30 dB, changing it
to 22 dB might be warranted.
Headphone Output Channel Routing
Choices are Left, Right, and Left and Right.
Two Dante receiver (input) channels can be assigned
to the headphone output channels using the Dante
Controller application. How these two audio signals
are route to the Model 370A’s headphone output
channels can be congured using this conguration
choice. The three options provide exibility in how
the audio sources are presented to the user. When
using a stereo (“double mu󰀨”) headset it’s common
for the audio input sources to be routed to both the
left and right channels. But the Model 370A’s exibility
allows each source to be independently congured
for sending to the left only, right only, or both left and
right headphone channels.
When using a stereo headset sending all inputs to
both channels is often referred to as a dual-channel
mono output. If a monaural (“single mu󰀨”) headset
is used the Left conguration option allows the two
input channels to be combined to monaural so that
the listener can simultaneously hear both sources.
Sidetone – Level
Choices are O, Low, Medium Low, Medium,
Medium High, and High.
The Model 370A includes a sidetone function that
allows microphone audio coming from the microphone
preamplier to be sent to the both channels of the
headphone output. This serves as a user conrma-
tion that they are actively sending audio to either or
both of the talk output channels. Sidetone audio will
only be routed to the headphone output when either
or both of the talk channels are active. The level of
the sidetone audio can be selected from among ve
values. The correct value is simply the one that makes
the user most comfortable. Sidetone audio can also
be disabled by selecting O. Selecting O would be
useful only in special applications such as during
troubleshooting or where user talk audio is being
returned as part of their listen audio signals. The two
rotary level controls will not impact the sidetone level.
Button Operation
Choices are Push to Talk, Latching, Push to Talk/
Tap to Latch, and Disabled.
This conguration section allows independent selec-
tion of how the two talk buttons will function. When
the Push to Talk mode is selected, the operation is
self-explanatory. Only when a talk button is pressed
and held will talk audio be sent out its associated
Dante transmitter (output) channel.
When the Latching mode is selected, tapping
(momentarily pressing) the button will cause the func-
tion to “latch” into the talk active mode. Tapping the
button again will cause the function to “unlatch” and
talk will no longer be active.
When the Push to Talk/Tap to Latch mode is selected,
a “hybrid” function of sorts is enabled. Pressing and
holding the talk button will enable audio to be sent
out its associated Dante transmitter (output) channel.
When the button is released, audio will stop being
sent out its associated transmitter channel. Tapping
(momentarily pressing) the button will cause the func-
tion to “latch” into the talk active mode. Tapping the
button again will cause the function to “unlatch” and
talk will no longer be active.
Many applications are best served when the buttons
are congured in the Push to Talk mode. This ensures
that a channel can’t accidentally be left in its talk active
mode. There are certainly valid situations when the
Latching or Push to Talk/Tap to Latch modes setting
will prove to be very useful.
When the Disabled mode is selected, microphone
audio will never be sent out the associated Dante
transmitter (output) channel. This can be useful when

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Model 370A
INTERCOM BELTPACK
the audio input associated with this channel is going
to be monitored but talk audio is not allowed to “join”
this specic intercom channel.
System – Mic Kill
Choices are O, Device ID, Global Kill Command,
and Device ID/Global Kill Command.
The mic kill function allows an enabled talk channel
to be disabled by remote control. Specically, it’s pos-
sible to remotely change all active (on) talk channels
to their o󰀨 state. This function is sometimes referred
to as a “talk o󰀨” function. There are two means avail-
able to remotely disable all active talk channels. The
Device ID method uses the identication command
generated by the Dante Controller or STcontroller
software applications as a “trigger” to disable any
active talk channels. The Global Kill Command can
be generated by applications that incorporate the
Studio Technologies’ proprietary method. This method
utilizes sending a data command over the Ethernet
connection. Select the desired mic kill conguration
from the four choices. Off simply means that no
remote talk control is supported.
Operation
At this point everything should be ready and Model
370A operation can commence. An Ethernet con-
nection with Power-over-Ethernet (PoE) capability
should have been made. A headset terminated with
a cable-mounted 5-pin male XLR connector should
be plugged into the headset connector.
Using the Studio Technologies’ STcontroller software
application the unit’s conguration should have been
selected to meet the needs of the specic application.
The Model 370A’s Dante conguration settings should
have been selected using the Dante Controller soft-
ware application. In this way, the Model 370A’s two
Dante audio transmitter (output) channels and two
Dante audio receiver (input) channels should have
been routed, by way of Dante “subscriptions,” to
the receiver and transmitter channels on associated
Dante-enabled equipment.
Initial Operation
The Model 370A will start to function as soon as a
Power-over-Ethernet (PoE) power source is con-
nected. However, it may take 20 to 30 seconds for
full operation to commence. Upon initial power up the
three status LEDs located on the bottom panel below
the etherCON RJ45 jack will begin to light as network
and Dante connections are established. The green
and orange LEDs that illuminate the three pushbutton
switches on the top panel may initially light randomly
and then will light in a test sequence to indicate that
the application rmware (embedded software) has
started. Once the entire sequence has completed
and the Dante connection has been established full
operation will begin.
Ethernet and Dante Status LEDs
Three status LEDs are located below the etherCON
RJ45 jack on the Model 370A’s bottom 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 Ethernet data
packet activity. The SYS and SYNC LEDs display the
operating status of the Dante interface and associated
network. The SYS LED will light red upon Model 370A
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 370A
is not synchronized with a Dante network. It will light
solid green when the Model 370A 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 370A is serving as the
Leader clock for the network. It’s possible that up to
30 seconds may be required for the SYNC LED to
reach its nal state.
Compressor Active LED
A yellow LED indicator is located on the bottom panel
adjacent to the headset connector. Labeled COMP,
the LED displays the status of the microphone audio
compressor function. It will light whenever the input
level from the microphone, along with the congured
preamplier gain, is such that the dynamic range of
the talk signal is being controlled. It’s perfectly accept-
able for this LED to light intermittently whenever a user
is talking at a normal voice level into the associated
microphone. But if the COMP LED lights solid while
a user is talking at a normal voice level this will typi-
cally indicate that the mic preamp gain setting should
be reduced. Conversely, if the COMP LED almost
never lights when normal talking is taking place, it’s
possible that changing the mic preamp gain to the

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INTERCOM BELTPACK
higher setting would be benecial. Note that due to
the design of the circuitry the compressor active LED
will function whether or not either or both of the talk
channels are active.
Headphone Output
Two rotary potentiometers (“pots”), located on the
Model 370A’s top panel, allow individual adjustment
of the level of the two audio input signals as they are
sent to the 2-channel headphone output. Depending
on the conguration of the unit, each audio input can
be sent to the left channel, the right channel, or both
the left and right channels of the headphone output.
The pots are “push in/push out” type which allow their
associated knobs to be in their “out” position to be
adjusted and then moved to their “in” position when
protection from an unwanted change is desired.
Users should nd the headphone output audio qual-
ity to be excellent, with high maximum output level
and low distortion. Audio signals do not pass directly
through the level pots. The position of the pots is
recognized by the Model 370A’s processor which
then adjusts the signal level within the digital domain.
When a pot is in its fully counterclockwise position
the associated audio signal is fully muted. The on/o󰀨
status of the two talk channels, or the status of the
call function, does not impact the headphone output.
Button Operation
Two pushbutton switches are associated with the
Model 370A’s two talk channels. How they function will
depend on the conguration of the unit. Each button
can be congured independently.
Push to Talk: When a button has been congured
for the Push to Talk mode, how it functions is pretty
self-explanatory. Press and hold the button when
headset microphone audio is to be sent out the
associated Dante audio transmitter (output) channel.
The button’s green LED will light to indicate that the
output is active. The button will not be lit when the
function is not active.
Latching: If a button has been configured for the
Latching mode, operation momentarily pressing (“tap-
ping”) the button will cause the function to change
states; o󰀨-to-on or on-to-o󰀨. Whenever the talk func-
tion is active the green LED will light. The button will
not be lit when the function is not active.
Push to Talk/Tap to Latch: If a button has been
congured for the Push to Talk/Tap to Latch mode,
operation is a bit di󰀨erent and certainly more exible.
Press and hold the button to activate the talk func-
tion. When released, the talk function will turn o󰀨.
Momentarily pressing (“tapping”) the button will cause
the function to change states; o󰀨-to-on or on-to-o󰀨.
Whenever the talk function is active the green LED
will light. The button will not be lit when the function
is not active.
Disabled: A button that is congured to the Disabled
mode will never allow talk audio to be sent to the as-
sociated Dante audio output channel. But to provide
“feedback” that the button has been pressed the
button’s green LED will ash rapidly three times. This
says, in e󰀨ect, “Yes, I recognize that you pressed the
button but I’m not going to do anything in response!”
Sidetone Function
The Model 370A includes a sidetone function that
sends microphone audio to the headphone output
channels whenever one or both of the talk buttons
are active. The quality of the sidetone audio should
be excellent and will provide Model 370A users with
a condence signal that they are actively talking to
other intercom users. Sidetone audio will always be
sent to both the left and right headphone channels
and is not a congurable choice. This is because the
function is trying to simulate what a user would hear
if they didn’t have a headset covering their ears. It is
not intended to indicate to the user which Dante audio
transmitter (output) channel or channels are actively
sending audio.
The exact sidetone level is congured from among
ve values within the STcontroller application. There
is also a selection choice for turning off sidetone.
There is no means of adjusting the sidetone level
using a physical button or control on the Model 370A
unit. Also, the two headphone level controls on the
top panel of the unit do not impact the sidetone level.
In most cases the exact sidetone level setting is not
critical and typical users will not be concerned about
revising it. But setting the sidetone level to something
reasonable is important. Setting the level too low will
encourage users to speak too loudly; setting it too
high and users will be tempted to speak hesitantly.
And while users aren’t provided with a sidetone level

Model 370A User Guide Issue 4. June 2023
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Model 370A
INTERCOM BELTPACK
control or other adjustment means, should the need
arise STcontroller allows rapid adjustment of the
sidetone level. In most cases the default sidetone
level, Medium, should provide an appropriate level.
Call Function
An integrated call function allows Model 370A users,
and users of compatible equipment, to signal to each
other visually. Individual call functions are provided for
each of the two talk channels. Either or both can have
its call function active at any one time. Technically, call
is achieved by sending a 20 kHz audio tone on the
desired audio output channel. This signal is summed
(mixed) with normal talk audio. The Model 370A’s
two audio input channels continually monitor for the
presence of 20 kHz. A call signal is recognized when
a continuous 20 kHz tone is detected on the audio
input for that channel.
Normal talk audio signals will not be confused with
a call signal. Digital lters within the Model 370A’s
processor integrated circuit limits the microphone
input’s high frequency response to about 10 kHz.
This helps to ensure that false call detection won’t
take place. Digital ltering is also performed on the
Dante audio receiver (input) signals before they are
sent to the headphone outputs. This prevents users
with extended high-frequency sensitivity, such as
hosts and guests associated with dog shows, from
receiving undesirable audio content.
To send a call signal is simple: just enable either or
both of the talk buttons and simultaneously press and
hold the call button. When call sending is active the
orange LED associated with the call button will light.
At the same time, the channel or channels that are
active in their talk mode will have their associated
orange LED ash. Release the talk button and/or the
call button and the sending of a call signal will cease.
As expected, pressing the call button when neither
talk channel is active will result in nothing occurring.
Whenever a Model 370A audio input channel receives
a call signal (20 kHz audio tone) the orange LED on
its companion talk button will rst ash and then light
continually. If a call signal is present on both audio
input channels then the orange LEDs on both talk
buttons will rst ash then remain lit. When receiving
a call signal on either or both audio input channels
the orange LED associated with the call button will
not light.
By using a 20 kHz tone for call signaling the Model
370A is compatible with legacy intercom equipment,
including the venerable RTS BP-325. When intercon-
necting Model 370A and BP-325 units using an ap-
propriate Dante-enabled interface, such as the Studio
Technologies’ Model 545DR Intercom Interface, call
signaling is fully compatible. Compatibility with the
Clear-Com method of call functionality is also pos-
sible by using the Model 545DC Intercom Interface.
(It converts the DC call signal associated with pin 3
of a Clear-Com party-line circuit to a 20 kHz tone.)
Also, devices such as the Studio Technologies’ Model
544D Audio Interface will send and receive 20 kHz
signals that are be compatible with the Model 370A.
The Model 544D converts its GPI (general-purpose
input) signals to 20 kHz tones and sums them with the
audio signals which are then transported “in band”
via the Dante audio paths. Audio signals received by
the Model 544D will be monitored for the presence of
20 kHz call signals. If call signals are detected the
GPO (general-purpose output) signals will activate.
How to Identify a Specic
Model 370A
The Dante Controller software application o󰀨ers an
Identify command that can be used to help locate a
specic Model 370A. When Identify is selected it will
send a command to a single Model 370A unit. On that
specic unit the three pushbutton LEDs (talk 1, talk
2, and call) will light in a unique pattern. In addition,
the SYS and SYNC status LEDs, located directly
below the etherCON RJ45 jack on the bottom panel,
will slowly ash green. After a few seconds the LED
identication pattern will cease and normal Model
370A button LED and Dante status LED operation
will resume.
If congured, the Identify command can also cause
the mic kill function to activate. For details please refer
to the next paragraph.
Mic Kill Function
The Model 370A includes a mic kill function, allowing
talk buttons that have been placed in their enabled
(on) state to be remotely changed to their disabled
(o󰀨) state. This allows one or both talk channels on
a specific Model 370A that have been enabled to
be remotely disabled. The reason for this function is
simple. It’s common in intercom applications for users
to enable a talk channel and then go “o󰀨 headset,”

Issue 4, June 2023 Model 370A User Guide
Page 14 Studio Technologies, Inc.
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INTERCOM BELTPACK
forgetting that they’ve left that talk channel enabled.
While they take a break or go to lunch, all other users
are forced to listen to that channel which may include
unwanted audio. Having the ability to disable this talk
channel can be very useful.
A congurable choice in the STcontroller software
application is used to select which of the mic kill
methods, Device ID or Global Kill Command, will be
recognized. Either or both can be enabled as desired.
It’s also possible to disable the mic kill function.
If the Device ID method of activating mic kill is
enabled, whenever a specic Model 370A is identied
using the Identify command within Dante Controller or
STcontroller any enabled talk channel will be forced to
its disabled state. If the Global Kill Command method
is enabled the Model 370A will respond to any such
request and force all talk channels to their disabled
state.
Technical Notes
IP Address Assignment
By default the Model 370A’s Ethernet interface will
attempt to automatically obtain an IP address and
associated settings using the DHCP (Dynamic Host
Configuration Protocol). If a DHCP server is not
detected an IP address will automatically be as-
signed using the link-local protocol. This protocol is
known in the Microsoft
®
world as Automatic Private IP
Addressing (APIPA). It is also sometimes referred to
as auto-IP. Link-local will randomly assign a unique
IP address in the IPv4 range of 169.254.0.1 to
169.254.255.254. In this way, multiple Dante-enabled
devices can be connected together and automatically
function, whether or not a DHCP server is active on
the LAN. Even two Dante-enabled devices that are
directly interconnected using an RJ45 patch cable will,
in most cases, correctly acquire IP addresses and be
able to communicate with each other.
An exception does arise when trying to directly inter-
connect two Dante-enabled devices that use Ultimo
integrated circuits to implement Dante. The Model
370A uses the Ultimo “chip” and, as such, a direct
one-to-one interconnection to another Model 370A
(or other Ultimo-based product) is not supported. An
Ethernet switch linking the two units is required to
successfully interconnect two Ultimo-based devices.
The technical reason that a switch is required relates
to the need for a slight latency (delay) in the data ow.
And an Ethernet switch will provide this. While this is
certainly an anomaly, since PoE power is required
for Model 370A operation it’s highly unlikely that an
application would use two Model 370A units without
a PoE-enabled Ethernet switch being present.
Using the Dante Controller software application
the Model 370A’s IP address and related network
parameters can be manually set for a xed (static)
conguration. While this is a more-involved process
than simply letting DHCP or link-local automatically
assign an address, if xed addressing is necessary
then this capability is available. In this case, it’s highly
recommended that each 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 370A’s IP address has been misplaced
there is no reset button or other method to easily
restore the unit to a default IP setting.
In the unfortunate event that a device’s IP address
is “lost,” the Address Resolution Protocol (ARP) net-
working command can be used to “probe” devices
on a network for this information. For example, in
Windows OS the arp –a command can be used to
display a list of LAN information that includes MAC
addresses and corresponding IP addresses. The
simplest means of identifying an unknown IP address
is to create a “mini” LAN with a small PoE-enabled
Ethernet switch connecting a personal computer to
the Model 370A. Then by using the appropriate ARP
command the required “clues” can be obtained.
Optimizing Network Performance
For best Dante audio-over-Ethernet performance
a network that supports VoIP Quality-of-service (QoS)
capability is recommended. This can be implement-
ed on virtually all contemporary managed Ethernet
switches. There are even specialized switches
that are optimized for entertainment-associated
applications. Refer to the Audinate website
(audinate.com) for details on optimizing networks for
Dante applications. Also, be certain to disable Energy-
E󰀩cient Ethernet (EEE) support on all Ethernet switch
ports that are associated with Dante devices. Some
implementations of EEE can incorrectly interpret that
a connected device is not present and prevent proper
Dante operation.

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Application Firmware Version
Display
There are two ways in which the version number of the
Model 370A’s application rmware (embedded soft-
ware) can be identied. One requires only the Model
370A unit and involves a button-press sequence
performed upon power up. The other method utilizes
the Model 370A and the STcontroller software appli-
cation. Either method may prove to be useful when
working with factory personnel on application support
and troubleshooting.
As part of the Model 370A’s power-up sequence
the unit’s application rmware (embedded software)
version number can be displayed. Before connecting
the PoE-enabled Ethernet cable, press and hold the
call button. Then connect the Ethernet cable. Upon
application of PoE power the Model 370A will go
through its normal power-up sequences followed by
a display of the rmware version. The LED associated
with the channel 1 talk button will “ash” to display
the major version number. Then the LED associated
with the channel 2 talk button will “ash” to display the
minor version number. Once the version number has
been displayed the call button can be released and
normal operation will begin. As an example of what
would be a typical application rmware display, if the
channel 1 talk button “ashes” two times followed
by the channel 2 talk button “ashing” one time this
would indicate that application rmware version 2.1
was present in the Model 370A.
A selection in the STcontroller software application
allows the Model 370A’s application rmware version
to be identied. Connect the Model 370A unit to the
network and let it connect and start to function. Then,
after starting STcontroller, review the list of identied
devices and select the specic Model 370A that inter-
ests you. Then select Version under the Device tab.
A page will then display that will provide lots of useful
information. This includes the application rmware
version and well as details on the rmware present
in the Ultimo integrated circuit.
Application Firmware Update
Procedure
It’s possible that updated versions of the application
rmware (embedded software) that is utilized by the
Model 370A’s processor (microcontroller or MCU)
integrated circuit will be released to add features or
to correct issues. Refer to the Studio Technologies’
website for the latest application rmware le. The
unit has the ability to load a revised le into the MCU’s
non-volatile ash memory by way of a USB recepta-
cle. The Model 370A implements a USB host function
that directly supports connection of a USB ash drive.
The Model 370A’s MCU updates its application rm-
ware using a le named M370A.bin.
The update process begins by preparing a USB ash
drive. The ash drive doesn’t have to be empty (blank)
but must be in the personal-computer-standard FAT32
format. Save the new application rmware le in the
root directory with a name of M370A.bin. Studio
Technologies will supply the application rmware le
inside a .zip archive le. While the application rm-
ware le inside of the zip le will adhere to the naming
convention required by the Model 370A, the name of
the zip le itself will include the le’s version number.
For example, a le named M370Av2.1MCU.zip would
indicate that version 2.1 of the application rmware
(M370A.bin) is contained within this zip le.
Once the USB ash drive is inserted into the USB
receptacle, located on the main circuit board under
the cover, the unit must be powered o󰀨 and again
powered on. At this point the le will automatically
be loaded into the processor’s ash memory. The
precise steps required will be highlighted in the next
paragraphs.
To update the application rmware le follow these
steps:
1.Disconnect power from the Model 370A. This will
entail removing the Ethernet connection that is
providing PoE power.
2. Remove the cover from the Model 370A. Begin by
removing the four Phillips-head machine screws (#1
screw driver tip), two per side. Be certain to save
the screws so that re-assembly will be fast and
painless. Then carefully slide the cover forward to
separate it from the level controls and buttons and
then lift it o󰀨.
3.Locate the USB receptacle on the main circuit
board. It’s near the call button. Insert the prepared
USB ash drive into it.
4. Apply power to the Model 370A by connecting to a
Power-over-Ethernet (PoE) Ethernet source.

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INTERCOM BELTPACK
5. After a few seconds the Model 370A will run a “boot
loader” program that will automatically load and
save the new application firmware file (M370A.
bin). This will take only a few seconds. During this
time period the call button’s LED will ash slowly
in alternating colors. Once the entire process is
over, taking approximately 10 seconds, the Model
370A will restart using the newly-saved application
rmware.
6. At this time the Model 370A is operating under the
newly-saved application firmware and the USB
ash drive can be removed. But to be conservative,
remove PoE power rst and then remove the USB
ash drive.
7. Conrm that the desired application rmware ver-
sion has been correctly saved. This can be done
by pressing and holding the call button, applying
PoE power to the Model 370A, and then “reading”
the application rmware version number by rst
observing the channel 1 talk button’s LED and then
observing the channel 2 talk button’s LED. Alter-
nately, the STcontroller software application can
be used to identify the application rmware version
number. Whatever method you use, ensure that the
desired version is present.
8.Once the update process has been completed
reverse the steps and reattached the cover using
the four machine screws.
Note that upon power being applied to the Model
370A if a connected USB ash drive doesn’t have the
correct le (M370A.bin) in the root folder no harm will
occur. If the correct le is not present upon power up
the call button’s LED will ash on and o󰀨 rapidly for a
few seconds to indicate this error condition and then
normal operation using the unit’s existing application
rmware will begin.
Ultimo Firmware Update
As previously discussed, the Model 370A implements
Dante connectivity using the 2-input/2-output Ultimo
integrated circuit from Audinate. The Dante Controller
software application can be used to determine the
version of the firmware (embedded software) that
resides in the Ultimo “chip.” The STcontroller software
application can also be used to identify the Ultimo’s
rmware version. (Use the Version selection under
the Device tab.) The Ultimo rmware can be updated
by way of the Model 370A’s Ethernet connection. The
latest Ultimo rmware le is available on the Studio
Technologies’ website. The Dante Firmware Update
Manager (FUM) application program can be used to
install the Ultimo rmware. The Dante Controller soft-
ware application also includes an automated method
of updating Ultimo rmware. It o󰀨ers a much simpler
method of keeping the Ultimo rmware current.
Model 370A versus Model 370
Some users may be interested in the differences
between the original Model 370 Intercom Beltpack
and the newer Model 370A that are described in this
guide. A comparison chart is available on the Studio
Technologies’ website. In addition, the following text
provides a summary of the changes:
• All configuration selections for the Model 370A
are performed using the STcontroller software
application. STcontroller also allows the version
numbers of the Model 370A’s application rmware
(embedded software) and Ultimo rmware to be
remotely identied.
• Support for electret microphones was added to
the Model 370A. This involved adding a 5 volt DC
power source to the microphone input circuitry.
This power source can be enabled or disabled as
required using STcontroller.
• The congurable microphone input gain settings
were modied to be compatible with the increased
output level supplied by electret microphones.
• The DIP switch assembly on the Model 370 is not
present on the Model 370A. As such, the belt clip
no longer needs to be rotated and its mounting
arrangement has been changed.
• The user-accessible sidetone trim potentiometer
found on the Model 370 is not present on the Model
370A. In the Model 370A the level of the sidetone
function is congured using STcontroller.
• The Model 370A o󰀨ers a second method of activat-
ing the mic kill function. This allows a data signal,
in addition to the Device ID command, to activate
mic kill.
• The STcontroller software application now o󰀨ers
the ability to congure the mic kill function, includ-
ing allowing it to be disabled.

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Model 370A
INTERCOM BELTPACK
Belt Clip
The belt clip is attached to the back of the Model
370A’s enclosure by way of two 6-32 thread, Philips-
head machine screws. Unlike other the original
Model 370 Intercom Beltpack units, the belt clip on
the Model 370A will never have to be rotated as part
of the conguration process. (There are no cong-
uration DIP switches under the belt clip.) But if the
belt clip does need to be replaced a #1 Philips-head
screw driver would be the correct tool to remove the
machine screws.
Restoring Factory Defaults
A command in the STcontroller software application
allows the Model 370A’s conguration to be reset to
the factory default values. From STcontroller select the
Model 370A for which you want to restore its defaults.
Select the Device tab and then select the Factory
Defaults feature. Then click on the OK box. Refer
to Appendix A for a list of the Model 370A’s factory
default values.

Issue 4, June 2023 Model 370A User Guide
Page 18 Studio Technologies, Inc.
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INTERCOM BELTPACK
Specications
Power Source:
Power-over-Ethernet (PoE): class 1 (very low
power, ≤3.84 watts) per IEEE®802.3af
Network Audio Technology:
Type: Dante audio-over-Ethernet
AES67-2013 Support: yes
Dante Domain Manager (DDM) Support: yes
Bit Depth: up to 24
Sample Rate: 48 kHz
Number of Transmitter (Output) Channels: 2
Number of Receiver (Input) Channels: 2
Dante Audio Flows: 4; 2 transmitter, 2 receiver
Network Interface:
Type: 100BASE-TX, twisted-pair Ethernet,
Power-over-Ethernet (PoE) supported
Data Rate: 100 Mb/s (10 Mb/s and 1000 Mb/s GigE
Ethernet not supported)
Audio Channels: 2 talk, 2 listen
Microphone Input:
Compatibility: dynamic or electret (low-voltage
DC-powered) microphones
Type: unbalanced
Electret Microphone Power: 3.3 volts DC via
2.00 k resistor, selectable on/off
Gain: 22, 30, 42, or 48 dB, selectable, ref. –60 dBu
input to Dante output (–20 dBFS nominal)
Frequency Response: 50 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.02%
Noise Floor: –95 dBFS (A-weighted)
Compressor:
Threshold: 1 dB above nominal level (–19 dBFS)
Slope: 2:1
Status LED: compressor active
Headphone Output:
Type: 2-channel
Compatibility: intended for connection to stereo
(dual-channel) or monaural (single-channel) head-
sets with nominal impedance of 50 ohms or greater
Maximum Output Voltage: 3.8 Vrms, 1 kHz,
150 ohm load
Frequency Response: 20 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.002%
Dynamic Range: >100 dB
Call Function:
Signaling Method: 20 kHz, ±800 Hz, within audio
channels
Call Send Level: –20 dBFS
Call Receive Level: –27 dBFS minimum
Connectors:
Headset: 5-pin female XLR
Ethernet: Neutrik NE8FBH etherCON RJ45 jack
USB: type A receptacle (located inside Model 370A’s
enclosure and used only for application rmware
updates)
Conguration: requires Studio Technologies’
STcontroller software application
Environmental:
Operating Temperature: 0 to 50 degrees C
(32 to 122 degrees F)
Storage Temperature: –40 to 70 degrees C
(–40 to 158 degrees F)
Humidity: 0 to 95%, non-condensing
Altitude: not characterized
Dimensions (Overall):
3.6 inches wide (9.2 cm)
1.6 inches high (4.0 cm)
4.8 inches deep (12.6 cm)
Mounting Options: intended for portable applica-
tions; contains integral belt clip; optional MBK-01
Mounting Bracket Kit allows Model 370A to be
permanently mounted
Weight: 0.6 pounds (0.3 kg)
Specifications and information contained in this
User Guide subject to change without notice.

Model 370A User Guide Issue 4. June 2023
Studio Technologies, Inc. Page 19
Model 370A
INTERCOM BELTPACK
Appendix A: STcontroller Default Conguration Values
STcontroller default Model 370A conguration values:
Microphone Input – Electret Power: O󰀨
Microphone Input – Gain: 42 dB
Headphone Output – Channel 1 Input Routes to: Left
Headphone Output – Channel 2 Input Routes to: Right
Sidetone – Level: Medium
Button Operation – Channels 1 and 2: Push to Talk/Tap to Latch
System – Mic Kill: Global Kill Command