Studio Technologies 372A User manual

50691-0623, Issue 2
Copyright © 2023 by Studio Technologies, Inc., all rights reserved
studio-tech.com
User Guide
Issue 2, June 2023
This User Guide is applicable for serial numbers
M372A-00151 and later with application rmware 2.1 and later
Model 372A
Intercom Beltpack

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Model 372A User Guide Issue 2. June 2023
Studio Technologies, Inc. Page 3
Model 372A
INTERCOM BELTPACK
Table of Contents
Revision History............................................................................................. 4
Introduction.................................................................................................... 5
Getting Started............................................................................................... 7
Dante Conguration....................................................................................... 9
Model 372A Conguration ............................................................................. 9
Operation...................................................................................................... 12
Technical Notes ............................................................................................ 14
Specications................................................................................................ 18
Appendix A: STcontroller Default Conguration Values ................................ 20

Issue 2, June 2023 Model 372A User Guide
Page 4 Studio Technologies, Inc.
Model 372A
INTERCOM BELTPACK
Revision History
Issue 2, June 2023:
• Adds screen capture for the STcontroller application.
• Miscellaneous improvements and clarications.
• Updated to meet latest document format.
Issue 1, April 2019:
• Initial release.

Model 372A User Guide Issue 2. June 2023
Studio Technologies, Inc. Page 5
Model 372A
INTERCOM BELTPACK
Introduction
The Model 372A Intercom Beltpack is a highly com-
pact user-worn device that combines a single channel
of talk and two channels of listen. The unit begins with
the features o󰀨ered by traditional analog party-line
(PL) 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
372A and other compatible Studio Technologies’ belt-
pack units can be used to create party-line intercom
applications with help from an external Dante-enabled
audio matrix such as the Studio Technologies’ Model
5422A Dante Intercom Audio Engine. Alternately,
Model 372A units can be used “point-to-point” or inter-
faced with Dante-compatible matrix intercom systems.
Having one talk and two listen channels may seem un-
conventional. But it can be ideal for many “real-world”
applications. Often an intercom user is primarily lis-
tening and non-verbally responding to requests made
by producers, directors, or stage managers. Typically,
the Model 372A will be congured to be part of one
talk-and-listen party-line intercom channel. During the
time that an event is taking place the listen function will
serve a much more important role; the talk function will
rarely be utilized. However, the second listen channel
will often be important. Typically, it will be designated
as a program-listen or “show audio” channel. The
two listen channels, along with the ability to receive
and display call signals, allow the Model 372A to very
e󰀨ectively support production personnel in a compact
and cost-e󰀨ective manner.
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 assign-
ment. Features include integrated sidetone, call signal
receive display, and remote mic kill (“talk o󰀨”). The
range of capabilities, along with the excellent audio
quality provided by the digital audio signal path, o󰀨ers
a unique and powerful user experience.
Setting up and conguring a Model 372A 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. The Model
372A is compatible with both broadcast and “gaming”
headsets.
A broadcast or intercom-style headset with a dynamic
or electret (DC-powered) microphone can be inter-
faced with the Model 372A using a 5-pin XLR connec-
tor. The Model 372A also directly supports connection
of earbuds or gaming headsets that utilize a 3.5 mm
4-conductor TRRS plug. These moderately priced
devices, commonly associated with mobile phones or
personal computers, are often of high-quality and may
be preferred for some applications. With the Model
372A’s moderate price and ability to support a broad
range of headset devices the overall cost of deploying
an intercom system can often meet budget goals.
The STcontroller software application is used to select
the unit’s operating parameters. The talk pushbutton
switch 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 372A’s compact 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 attach-
ment to a user’s clothing.
Figure 1. Model 372A Intercom Beltpack top and bottom views

Issue 2, June 2023 Model 372A User Guide
Page 6 Studio Technologies, Inc.
Model 372A
INTERCOM BELTPACK
The audio quality of the Model 372A is excellent, with
low distortion, low noise, and high headroom. Careful
circuit design and rugged components ensure long,
reliable operation. A wide range of applications can
be supported, including education and commercial
theater, sports and entertainment TV and radio
events, streaming broadcasts, corporate and govern-
ment AV, post production, and aerospace.
Dante Audio-over-Ethernet
Audio data is sent to and received from the Model
372A using the Dante audio-over-Ethernet media
networking technology. As a Dante-compliant device,
the Model 372A’s one Dante audio transmitter (output)
channel and two Dante audio receiver (input) chan-
nels can be interconnected (routed) with other devices
using the Dante Controller software application. The
Dante transmitter (output) and receiver (input) chan-
nels 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 372A
is AES67 compatible and compliant with the Dante
Domain Manager™ software application.
Two bi-color LEDs provide status indications of the
Dante interface. The Dante Identify command takes
on a unique role with the Model 372A. Not only will it
cause the talk pushbutton’s orange LED to light in a
highly visible sequence, it will also turn o󰀨 (“kill”) the
talk function if it is active.
Audio Quality
The Model 372A offers “pro” audio performance
that is not found in typical party-line (PL) intercom
beltpacks. A low-noise, wide dynamic-range mi-
crophone preamplifier and associated voltage-
controlled-amplier (VCA) dynamics controller (com-
pressor) ensures that microphone audio quality is
preserved while minimizing the chance of signal
overload. DC power to support electret microphones
can be enabled as required. The output of the mi-
crophone preamp and compressor is routed to an
analog-to-digital converter (ADC) section that sup-
ports 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 372A’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.
Call Function Receive
A call receive function allows Model 372A users to be
provided with a visual indication that a call signal is
active. The orange LED within the pushbutton switch
will rst ash then light solid whenever a call signal
is detected on either of the Dante receiver (input)
channels. Using 20 kHz tones, the call signals are sent
within the Dante audio channels (“in band”) allowing
interoperability between multiple Studio Technologies’
beltpack 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 372A 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 372A by way of an Ethernet
network connection. Congurable parameters include
microphone power and preamplier gain, headphone
monitoring, sidetone audio operation, and talk button
operation.
The microphone input can be selected for compati-
bility with dynamic or electret (DC-powered) micro-
phones. The gain of the microphone preamplier can
be selected from among ve choices. These choices
allow compatibility with the variety of microphones
that are part of broadcast, intercom, and computer
gaming headsets.

Model 372A User Guide Issue 2. June 2023
Studio Technologies, Inc. Page 7
Model 372A
INTERCOM BELTPACK
To support optimum user performance, the Model
372A’s talk pushbutton switch can be configured
from among three choices: Push to Talk, Latching, or
Push to Talk/Tap to Latch. Two audio channels arrive
via Dante receivers (inputs) and are destined for the
2-channel headphone output. Each input source can
be independently routed to the left headphone chan-
nel, right headphone channel, or both the left and right
headphone channels. This exibility allows a variety of
listening environments to be created, including stereo,
single-channel monaural, and dual-channel monaural.
Ethernet Data and PoE
The Model 372A connects to an Ethernet data net-
work using a standard 100 Mb/s twisted-pair Ethernet
interface. The physical interconnection is made by
way of a Neutrik
®
etherCON RJ45 jack. While com-
patible 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 372A’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 372A’s PoE interface reports to the power
sourcing equipment (PSE) that it’s a class 1 (very low
power) device.
Future Capabilities and Firmware
Updating
The Model 372A 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 372A 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 372A
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 may be made
using the three connectors located on the bottom
of the Model 372A’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. Alternately, a headset with a 3.5 mm
4-conductor TRRS plug can be used. (The headset’s
plug needs to follow the CTIA™/AHJ conguration
standard.)
Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that supports
Power-over-Ethernet (PoE) is required for Model
372A operation. This one connection will provide
both the Ethernet data interface and power for the
Model 372A’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 372A 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 372A’s enclosure. This allows
connection by way of a cable-mounted etherCON
connector or a standard RJ45 plug. The Model 372A’s
Ethernet interface supports auto MDI/MDI-X so that
a crossover cable is not required.
Headset Connections
The Model 372A allows two di󰀨erent types of headsets
to be connected. A 5-pin female XLR connector is
provided to support connection of a standard broad-
cast- or intercom-style communications headset. A
3.5 mm 4-conductor TRRS jack allows a computer
gaming headset to be directly connected. The Model

Issue 2, June 2023 Model 372A User Guide
Page 8 Studio Technologies, Inc.
Model 372A
INTERCOM BELTPACK
372A’s two headset connectors are electrically wired
in parallel. As such, only one type of headset should
be connected at one time.
Headset A
The Model 372A provides a 5-pin female XLR
connector that interfaces with the microphone and
headphone connections of a single- or dual-ear
intercom- or broadcast-style headset. The connector
is labeled Headset A. Refer to Figure 2 for connec-
tion 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 correctly if its signal – (low) is connected to
Model 372A’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 monau-
ral output. It’s important not to connect together (short)
pins 4 and 5 of the headset’s connector as damage to
the Model 372A’s output circuitry could result.
A monaural (single-earpiece or “single mu󰀨”) headset
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 inter-
connecting cable assemblies terminate the earpiece’s
left and right connections opposite from what the
Model 372A and other broadcast equipment require.
These cables may terminate the left earpiece to pin
5 of the 5-pin male XLR connector and the right ear-
piece to pin 4. If this condition is present it will require
reversing or “ipping” the two wires in a headset’s
connector such that the left earpiece connects to
pin 4 and the right earpiece to pin 5.
If a separate microphone and pair of headphones
need to connected an adapter cable assembly should
be fabricated. It would consist of a 5-pin male XLR
connector wired to both a 3-pin female XLR connector
for the microphone and a ¼-inch or 3.5 mm TRS jack
for the headphones. In this scenario, the microphone
would in most cases be a dynamic type as the Model
372A provides only low-voltage DC “electret” power.
Phantom-powered (P12 or P48) microphones would
not be compatible. Most hand-held or “stick” micro-
phones are dynamic and should function correctly.
Headset B
The Model 372A also allows direct connection of
gaming headsets that are ubiquitous in the personal
computer world. The 3.5 mm 4-conductor TRRS jack,
labeled Headset B, is compatible with the CTIA™/
AHJ conguration standard which has the headphone
left channel on the tip connection, the headphone
right channel on the ring 1 connection, common on
the ring 2 connection, and the microphone on the
sleeve connection. Compatible headsets are readily
available, typically described as personal computer
or gaming headsets. The microphones used in these
headsets are electret type which require a low-voltage
DC source for operation. The Model 372A is able to
provide this power and requires only that the appro-
priate setting in STcontroller be selected. Refer to
Figure 3 for a detailed description of the compatible
TRRS plug.
Figure 2. Headset A connection pinout chart Figure 3. Headset B connection pinout chart

Model 372A User Guide Issue 2. June 2023
Studio Technologies, Inc. Page 9
Model 372A
INTERCOM BELTPACK
Dante Conguration
For audio to pass to and from the Model 372A requires
that several Dante-related parameters be congured.
These conguration settings will be stored in non-
volatile memory within the Model 372A’s circuitry.
Conguration 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 372A
uses the Ultimo 2-input/2-output integrated circuit to
implement the Dante architecture. One transmitter
(output) channel and both receiver (input) channels
are utilized.
The Dante transmitter (output) channel associated
with the Model 372A’s Dante interface must be as-
signed to the desired Dante receiver (input) channel.
This achieves routing the Model 372A’s one talk out-
put audio channel to the device (or devices) that will
be “listening” to it. Within Dante Controller a “subscrip-
tion” 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 372A’s Dante
transmitter (output) channel needs 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 372A’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 372A’s 2-channel
headphone output.
The Model 372A supports an audio sample rate of
48 kHz with no pull-up/pull-down values available.
The Model 372A can serve as the Leader clock or 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 372A has a default Dante device name
of ST-M372A- followed by a unique su󰀩x. The suf-
fix identifies the specific Model 372A that is being
congured. The su󰀩x’s actual alpha and/or numeric
characters relate to the MAC address of the unit’s
Ultimo integrated circuit. The one Dante transmitter
(output) channel has a default name of Ch1. 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 372A Conguration
Many of the Model 372A’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 des-
ignated personal computer. This personal computer
must be on the same local area network (LAN) and
subnet as the Model 372A unit or units that are to be
congured.
Changes made using STcontroller will be immediately
reected in the unit’s operation; no Model 372A “re-
boot” is required. Each time a change is made the talk
button, located on the top panel, will momentarily ash
orange to indicate that a command from STcontroller
has been received.

Issue 2, June 2023 Model 372A User Guide
Page 10 Studio Technologies, Inc.
Model 372A
INTERCOM BELTPACK
Using STcontroller
Immediately after starting STcontroller the application will locate and display the devices that it can control. All
Model 372A units that are present on the network will be recognized and display on the device list. Use the
Identify command to allow easy recognition of a specic Model 372A 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
requires a source of low-voltage DC power for opera-
tion enable the Electret Power check box. In virtually
all cases a gaming or computer headset that uses a
3.5 mm TRRS plug will require microphone power. If
the associated headset has a dynamic (non-powered)
microphone do not enable the Electret Power check
box. Most broadcast headsets that terminate on 5-pin
male XLR connectors 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 A connector.
Note that the Model 372A 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 24 dB, 30 dB, 36 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 36, 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 24 and 30 dB gain
settings will typically be appropriate for use with this
type of microphone.

Model 372A User Guide Issue 2. June 2023
Studio Technologies, Inc. Page 11
Model 372A
INTERCOM BELTPACK
When a dynamic microphone is connected to the
Model 372A the 42 dB gain setting should be appro-
priate for many applications. The 36 dB choice may
be correct should the connected microphone have a
high sensitivity (high output level for a given acoustical
input) or an enthusiastic user routinely talks loudly into
the microphone. 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 372A
is going to be deployed at events where users are not
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 24 or 30 dB gain setting will probably
be appropriate in these cases.
The compressor active LED, labeled COMP and
visible adjacent to the HEADSET A 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 24 dB might be warranted.
Headphone Output Channel Routing
Choices are Left, Right, and Left and Right.
Two Dante transmitter (output) channels can be
assigned to the Model 372A’s two Dante receiver
(input) channels using the Dante Controller appli-
cation. How these two audio signals are routed to
the Model 372A’s headphone output channels can
be independently configured. For flexibility, each
input source has three routing options. They can be
independently congured for sending only to the left
channel, only to the right channel, or sending to both
the left and right headphone output channels.
In some applications, split-mono or stereo operation
will be desired. In this case, input channel 1 might be
routed to the left headphone output while input chan-
nel 2 might be routed to the right headphone output.
When using a stereo or dual-ear headset sending
both inputs to both headphone output 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 and sent to just the left
headphone output channel.
Sidetone – Level
Choices are O, Low, Medium Low, Medium,
Medium High, and High.
The Model 372A includes a sidetone function that
allows microphone audio coming from the micro-
phone input section to be sent to the headphone
output. This serves as a user conrmation that they
are actively sending audio to the talk output channel.
Sidetone audio will only be routed to the headphone
output when the talk channel is 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 – Talk
Choices are Push to Talk, Latching, and Push to
Talk/Tap to Latch.
This conguration section allows selection of how the
talk button will function. When the Push to Talk mode
is selected, the operation is self-explanatory. Only
when the talk button is pressed and held will talk audio
be sent out the 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 the Dante transmitter (output) channel. When the
button is released, audio will stop being sent out the
transmitter channel. Tapping (momentarily pressing)
the button will cause the function to “latch” into the talk
active mode. Tapping the button again will cause the
function to “unlatch” and talk will no longer be active.

Issue 2, June 2023 Model 372A User Guide
Page 12 Studio Technologies, Inc.
Model 372A
INTERCOM BELTPACK
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 mode or Push to Talk/Tap to Latch mode
settings will prove to be very useful.
Operation
At this point everything should be ready and Model
372A 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 may be
plugged into the Headset A connector. Alternately, a
gaming or computer-type headset will be connected
to Headset B using a 3.5 mm 4-conductor TRRS plug.
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 372A’s Dante conguration settings should
have been selected using the Dante Controller soft-
ware application. In this way, the Model 372A’s Dante
audio transmitter (output) channel and two Dante au-
dio 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 372A 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
compressor active LED might somewhat randomly
ash for a brief period. The green and orange LEDs
that illuminate the talk pushbutton switch will light as
part of a short test sequence to indicate that the ap-
plication rmware (embedded software) has started.
The mic power LED will also light for a short interval to
indicate that it is functioning. Once the test 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 372A’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 372A
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 372A
is not synchronized with a Dante network. It will light
solid green when the Model 372A 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 372A 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 A connector. Labeled
COMP, the LED displays the status of the microphone
preamplier 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 perfect-
ly acceptable for this LED to light intermittently when-
ever a user is talking at a normal voice level into the
connected microphone. But if the COMP LED lights
solid while a user is talking at a normal voice level this
will typically 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 higher setting would be benecial. Note
that due to the design of the circuitry the compressor
active LED will function whether or not the talk chan-
nel is active.
Headphone Output
Two rotary potentiometers (“pots”), located on the
Model 372A’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

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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 372A’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/
off status of the talk channel does not impact the
headphone output.
Button Operation
A pushbutton switch is associated with the Model
372A’s talk channel. How the switch functions will
depend on the conguration of the unit.
Push to Talk: When the 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 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 the button has been congured 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 the 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 pushbutton
will light green. The button will not be lit when the
function is not active.
Sidetone Function
The Model 372A includes a sidetone function that
sends microphone audio to the headphone output
whenever the talk function is active. The quality of the
sidetone audio should be excellent and will provide
Model 372A 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 output channels. This is because the
function is trying to simulate what a user would hear
if they didn’t have a headset covering both their ears.
An exception is if both Dante input channels are
routed to only the left headphone output channel. In
this case, sidetone audio will only be sent to the left
headphone output channel.
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 372A
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 typically 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
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 Detection Display
A Model 372A function allows a call signal that’s
present on either Dante receiver (input) channel to
cause the pushbutton switch’s LED to light. Whenever
a call signal is detected the button’s orange LED will
rst ash and then light continually. Technically, a call
signal is achieved by sending a 20 kHz audio tone
on the desired Dante audio channel. This signal is
summed (mixed) with normal talk audio. The Model
372A’s two audio input channels continually monitor
the audio input for the presence of 20 kHz.

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The detection circuitry will not confuse normal talk
audio signals with a call signal. Digital lters with-
in the Model 372A’s processor integrated circuit
help to ensure that false call detection won’t take
place. Digital ltering is also performed on the mi-
crophone audio output signals as well as 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.
By using a 20 kHz tone for call signaling the Model
372A is compatible with legacy intercom equipment,
including the venerable RTS BP-325 beltpack. When
interconnecting Model 372A and BP-325 units using
an appropriate Dante-enabled interface, such as the
Studio Technologies’ Model 545DR Intercom Inter-
face, call signaling is fully compatible. Compatibility
with the Clear-Com
®
method of call functionality is
also possible 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
372A. 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.
How to Identify a Specic
Model 372A
Both the Dante Controller and STcontroller software
applications o󰀨er a command that can be used to
help locate a specic Model 372A. When the Identify
command is selected it will send a message to a single
Model 372A unit. On that specic unit the pushbutton
switch’s orange LED will ash rapidly. 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
372A button LED and Dante status LED operation
will resume.
Mic Kill Support
The Model 372A includes a mic kill function, allowing
the talk button, if it has been placed in its enabled (on)
state, to be remotely forced to its disabled (o󰀨) state.
This function is sometimes referred to as a “talk o󰀨”
function. Two actions can enable the mic kill function.
Any time a Model 372A receives a Dante Identify com-
mand it will cause both an LED pattern to start as well
as enabling the mic kill function. The second “trigger”
method uses the Studio Technologies’ Global Mic Kill
command. This command can be activated from a
menu choice in the STcontroller software application.
The reason for the Model 372A to o󰀨er a mic kill func-
tion is simple. It’s common in intercom applications
for users to enable (“latch on”) a talk channel and
then go “o󰀨 headset,” 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. This
makes having the ability to disable a talk channel
very useful. The Dante Identify command allows a
“latched on” talk channel on a specic Model 372A to
be remotely disabled. Alternately, by using the Global
Mic Kill command a large group of units can simulta-
neously have their talk channels disabled. This would
include any Studio Technologies’ compatible device
that follows this protocol.
Technical Notes
IP Address Assignment
By default, the Model 372A’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
372A uses Ultimo and a design limitation in it prevents
a one-to-one interconnection with another Model 372A

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Model 372A
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(or any other Ultimo-based product). An Ethernet
switch linking the two Ultimo-based units is required to
successfully interconnect them. The technical reason
that a switch is required relates to the need for a slight
latency (delay) in the data ow; an Ethernet switch
will provide this. While this is certainly an anomaly,
since PoE power is required for Model 372A operation
it’s highly unlikely that an application would use two
Model 372A units without a PoE-enabled Ethernet
switch being present.
Using the Dante Controller software application,
the Model 372A’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 IP address, if xed IP addressing is nec-
essary 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 372A’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 Win-
dows 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 372A.
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 appli-
cations. 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 Dante device is not present and prevent
proper operation.
Application Firmware Version
Display
There are two ways in which the version number of the
Model 372A’s application rmware (embedded soft-
ware) can be identied. One requires only the Model
372A unit and involves a button-press sequence
performed upon power up. The other method utilizes
the Model 372A 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 372A’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
talk pushbutton. Then connect the Ethernet cable.
Upon application of PoE power the Model 372A will
go through its normal power-up sequences followed
by a display of the rmware version. The LED asso-
ciated with the talk button will “ash” green to display
the major version number. Then, after a short pause,
the talk button’s LED will “ash” orange to display the
minor version number. Once the version number has
been displayed the talk button can be released and
normal operation will begin. As an example of what
would be a typical application rmware display, if the
LED in the talk button rst “ashes” green two times
then “ashes” orange one time this would indicate
that application rmware version 2.1 was present in
the Model 372A.
A selection in the STcontroller software application
allows the Model 372A’s application rmware version
to be identied. Connect the Model 372A 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 372A that inter-
ests you. Then select Version under the Device tab.
A page will then display that will provide a lot of useful
information. This includes the application rmware
version and well as details on the rmware present
in the Ultimo integrated circuit.

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Application Firmware Update
Procedure
It’s possible that updated versions of the application
rmware (embedded software) that is utilized by the
Model 372A’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 its MCU’s
non-volatile ash memory by way of a USB recepta-
cle. The Model 372A implements a USB host function
that directly supports connection of a USB ash drive.
The Model 372A’s MCU updates its application rm-
ware using a le named M372A.bin. (Note for geeks:
the su󰀩x .bin indicates that it’s a binary le.)
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 M372A.bin. Studio
Technologies will supply the application firmware
file inside a .zip archive file. While the application
rmware le inside of the zip le will adhere to the
naming convention required by the Model 372A, the
name of the zip le itself will include the le’s version
number. For example, a le named M372Av2r1MCU.
zip would indicate that version 2.1 of the application
rmware (M372A.bin) is contained within this zip le.
Once a correctly prepared USB ash drive is inserted
into the USB receptacle, located under the cover of
the Model 372A’s main circuit board, the unit must be
powered o󰀨 and again powered on. At this point the
le will automatically be loaded into the processor’s
flash memory. The precise steps required will be
highlighted in the following paragraphs.
To update the application rmware le follow these
steps:
1.Disconnect power from the Model 372A. This will
entail removing the Ethernet connection that is
providing PoE power.
2. Remove the cover from the Model 372A. 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 pushbutton
and then lift it o󰀨.
3.Locate the USB receptacle on the main circuit
board. It’s near the front, adjacent to the pushbutton
and level controls. Insert the prepared USB ash
drive into the USB receptacle.
4. Apply power to the Model 372A by connecting to a
Power-over-Ethernet (PoE) Ethernet source.
5. After a few seconds the Model 372A will run a “boot
loader” program that will automatically load and
save the new application rmware le (M372A.bin).
This will take only a few seconds. During this time
period the talk pushbutton’s LED will ash slowly
in alternate colors. Once the entire process is over,
taking approximately 10 seconds, the Model 372A
will restart using the newly saved application rm-
ware.
6. At this time the Model 372A 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.Confirm that the desired application firmware
version has been correctly saved. This can be
done by pressing and holding the talk pushbutton,
applying PoE power to the Model 372A, and then
“reading” the application rmware version number
by observing the talk pushbutton’s LED. Alternately,
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
372A, if a connected USB ash drive doesn’t have the
correct le (M372A.bin) in the root folder no harm will
occur. If the correct le is not present upon power up
the talk pushbutton’s LED will ash rapidly, alternating
green and orange, for a few seconds to indicate this
error condition after which normal operation using the
unit’s existing application rmware will begin.
Ultimo Firmware Update
As previously discussed, the Model 372A 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

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Model 372A
INTERCOM BELTPACK
version of the firmware (embedded software) that
resides in the Ultimo “chip.” The STcontroller software
application can also be used to identify Ultimo’s rm-
ware version. (Use the Version selection under the
Device tab.) The Ultimo rmware can be updated by
way of the Model 372A’s Ethernet connection. The
latest Ultimo rmware le is available on the Studio
Technologies’ website. The Dante Firmware Update
Manager (FUM) application program has traditionally
been used to install the Ultimo rmware. The Dante
Controller software application also includes an
automated method of updating Ultimo firmware.
Both applications are available, free of charge, on the
Audinate website (audiante.com).
Restoring Factory Defaults
A command in the STcontroller software application
allows the Model 372A’s conguration to be reset to
the factory default values. From STcontroller select the
Model 372A 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 372A’s factory
default values.

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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: 1
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)
Compatibility – Headset A: single- or dual-ear
broadcast-style with dynamic or electret (low-voltage
DC-powered) microphone: pin 1 mic common; pin 2
mic; pin 3 phones common; pin 4 phones left; pin 5
phones right
Compatibility – Headset B: CTIA™/AHJ congura-
tion (typically uses electret powered mic): tip phones
left; ring 1 phones right; ring 2 common; sleeve mic
Audio Channels: 1 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/o󰀨
Impedance: 1 k ohms, nominal, microphone power
o󰀨; 690 ohms, nominal, microphone power on
Gain: 24, 30, 36, 42, or 48 dB, selectable, ref.
–60 dBu input to Dante output (–20 dBFS nominal)
Frequency Response: 40 Hz to 20 kHz, –3 dB
Distortion (THD+N): <0.02% (at minimum gain)
Dynamic Range: 91 dB of dynamic range
Compressor:
Application: applies to Dante transmitter (output)
channel and sidetone audio
Threshold: 2 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: 2.8 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 Receive Function:
Implementation: monitors both Dante receiver
(input) channels for presence of call signals
Signaling Method: 20 kHz, ±800 Hz, within audio
channels
Call Receive Level: –27 dBFS minimum
Connectors:
Headset A: 5-pin female XLR
Headset B: 4-conductor (TRRS) 3.5 mm jack,
per Japanese standard JEITA/EIAJ RC-5325A
Ethernet: Neutrik NE8FBH etherCON RJ45 jack
USB: type A receptacle (located inside Model 372A’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

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Model 372A
INTERCOM BELTPACK
Dimensions (Overall):
3.1 inches wide (7.9 cm)
1.5 inches high (4.0 cm) without belt clip;
1.8 inches (4.6 cm) with belt clip
4.9 inches deep (12.5 cm)
Deployment: intended for portable applications;
contains integral belt clip
Weight: 0.5 pounds (0.23 kg)
Specications and information contained in this
User Guide subject to change without notice.

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Page 20 Studio Technologies, Inc.
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Appendix A: STcontroller Default Conguration Values
STcontroller default Model 372A conguration values:
Microphone Input – Electret Power: O󰀨
Microphone Input – Gain: 36 dB
Headphone Output – Channel 1 Input Routes to: Left
Headphone Output – Channel 2 Input Routes to: Right
Headphone Output – Sidetone Level: Medium
Button Operation – Talk: Push to Talk/Tap to Latch