Studio Technologies 370A User manual

Copyright © 2019 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50636-0819, Issue 2
User Guide
Issue 2, August 2019
This User Guide is applicable for serial numbers
M370A-02501 and later with application firmware 1.2 and later
Model 370A Intercom Beltpack

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Model 370A User Guide Issue 2, August 2019
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Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 8
Operation ...................................................................... 13
Technical Notes ............................................................. 17
Specifications ................................................................ 22
Appendix A .................................................................... 23

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Revision History
Issue 2, August 2019:
1. Documents revision to STcontroller (version 2.02.00 and later) which separates
microphone power and microphone gain configuration.
Issue 1, June 2018:
1. Initial release.

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Introduction
The Model 370A Intercom Beltpack begins
with the features offered by traditional 2-
channel party-line intercom user devices
and adds a range of new capabilities,
along with the advanced performance and
flexibility that Dante® audio-over-Ethernet
provides. 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 5422 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 us-
ing the STcontroller software application.
Configurable parameters include electret
microphone powering, microphone pre-
amplifier gain, talk button operation, and
headphone channel assignment. User
features include integrated sidetone, call
function, and remote mic kill (“talk off”).
The wide range of capabilities, along with
the excellent audio quality provided by the
digital audio signal path, offers a unique
and powerful user experience.
Set up and configuration of the Model 370A
is simple. An etherCON® RJ45 receptacle
is used to interconnect with a standard
twisted-pair Ethernet port associated with
a local-area network (LAN). This connec-
tion provides both power and bidirectional
digital audio. A broadcast or intercom-style
stereo or monaural headset with a dynamic
or electret (DC-powered) microphone
interfaces with the unit using a 5-pin XLR
connector.
The STcontroller software application is
used to select the unit’s operating param-
eters. Two talk pushbutton switches can
be configured for optimal operation. Two
push-in/push-out (“pop out”) rotary con-
trols make it easy to set and maintain the
desired headphone output level. The Model
370A’s enclosure is made from an alumi-
num alloy which offers 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 distor-
tion, low noise, and high headroom. Care-
ful circuit design and rugged components
ensure long, reliable operation. A wide
range of applications can be supported,
including sports and entertainment TV and
radio events, streaming broadcasts, corpo-
rate and government AV installations, and
post-production facilities.
Figure 1. Model 370A Intercom Beltpack top and bottom views

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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 audio output (Dante transmitter)
and two audio input (Dante receiver) chan-
nels can be interconnected (routed) with
other devices using the Dante Controller
software application. The Dante transmit-
ter and receiver channels are limited to
supporting four Dante flows, 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 com-
pliant 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 configured to turn off any
active talk channels.
Audio Quality
The Model 370A’s completely “pro” per-
formance is counter to the less-than-stellar
reputation of typical party-line (PL) intercom
audio. A low-noise, wide dynamic-range
microphone preamplifier and associated
voltage-controlled-amplifier (VCA) dynam-
ics controller (compressor) ensures that
microphone audio quality is preserved
while minimizing the chance of signal over-
load. DC power to support electret micro-
phones can be enabled if necessary.
The output of the microphone 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 pre-
pared for transport over Ethernet.
Audio input signals arrive via two Dante re-
ceiver 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
creation are performed within the digital
domain. This provides flexibility, allowing
precise control of the audio signals and
eliminating the need for the two rotary lev-
el controls from having to directly handle
analog audio signals. The audio signals
destined for the 2-channel headphone out-
put 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, head-
phones, and earpieces.
Call Function
A call function allows Model 370A users
to send and receive channel-specific vi-
sual alert signals. Pressing the call push-
button on the top of the unit is all that’s
required to signal other users that atten-
tion is requested. Using 20 kHz tones, the
call signals are sent within the audio chan-
nels (“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.

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Configuration Flexibility
A highlight of the Model 370A is its ability
to be easily configured to meet the needs
of specific users and applications. All
configuration choices are made using the
STcontroller software application that com-
municates with the Model 370A by way
of an Ethernet network connection. Con-
figurable parameters include microphone
power and preamplifier gain, sidetone
audio operation, talk button operation,
and headphone monitoring.
The microphone input can be selected
for compatibility with dynamic or elected
(DC-powered) microphones. The gain of
the microphone preamplifier can be se-
lected from among four choices. These
allow compatibility with the variety of mi-
crophones that are part of broadcast and
intercom headsets.
A unique Model 370A feature is the ability
to individually configure the way in which
the two talk pushbutton switches function;
four choices are available. For standard
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 destined for the 2-channel headphone
output. Each input source can be inde-
pendently routed to the left headphone
channel, right headphone channel, or both
the left and right headphone channels.
This flexibility allows a variety of listening
environments to be created, including ste-
reo, single-channel monaural, and dual-
channel monaural.
Ethernet Data and PoE
The Model 370A connects to an Ethernet
data network using a standard 100 Mb/s
twisted-pair Ethernet interface. The physi-
cal interconnection is made by way of
a Neutrik® etherCON RJ45 receptacle.
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 ef-
ficient interconnection with the associated
data network. To support PoE power man-
agement, the Model 370A’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 370A was designed such that
its capabilities and performance can be
enhanced in the future. A USB connector,
located on the unit’s main circuit board
(underneath the unit’s cover), allows the
application firmware (embedded software)
to be updated using a USB flash drive.
The Model 370A uses Audinate’s Ultimo™
integrated circuit to implement the Dante
interface. The firmware in this integrated
circuit can be updated via the Ethernet
connection, helping to ensure that its
capabilities remain up to date.

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Getting Started
What’s Included
Included in the shipping carton are a Model
370A Intercom Beltpack and a printed copy
of this guide. As a device that is Power-
over-Ethernet (PoE) powered, no external
power source is provided. In most applica-
tions 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 enclo-
sure. 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 Ether-
net data interface and power for the Model
370A’s circuitry. A 10BASE-T connection is
not sufficient and a 1000BASE-T (“GigE”)
connection is not supported unless it can
automatically “fall back” to 100BASE-TX
operation. The Model 370A supports Eth-
ernet switch power management, enumer-
ating itself as a PoE class 1 device. Any
source that is compliant with the IEEE®
802.3af standard will function correctly.
Should the selected Ethernet switch port
support Energy-Efficient 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 recep-
tacle that is located on the bottom of the
Model 370A’s enclosure. This allows con-
nection by way of a cable-mounted ether-
CON connector or a standard RJ45 plug.
The Model 370A’s Ethernet interface sup-
ports auto MDI/MDI-X so that a crossover
cable will never be required.
Headset Connection
The Model 370A provides a 5-pin female
XLR connector that interfaces with the
microphone and headphone 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) mi-
crophones. A balanced dynamic micro-
phone should, in most cases, also function
correctly 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 muff”) headsets to hear a monau-
ral 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
Figure 2. Headset connection pinout chart

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always be wired to pin 4 and the right
headphone channel to pin 5. Configura-
tion choices, discussed later in this guide,
can then be used to create the desired
monaural output. It’s important not to con-
nect together (short) pins 4 and 5 of the
Model 370A’s headset connector as dam-
age to the Model 370A’s output circuitry
could result.
Monaural (single-earpiece or “single
muff”) headsets should be wired such that
its headphone is wired only to pin 4; pin 5
should be remain unused. Configuration
choices, discussed later in this guide, can
be used to create a monaural output.
It’s possible that some Beyerdynamic
headset interconnecting cable assemblies
terminate the earpiece’s left and right con-
nections opposite from what the Model
370A and other broadcast equipment
require. These cables may terminate the
left earpiece to pin 5 of the XLR connec-
tor and the right earpiece to pin 4. If this
condition is present it will require reversing
or “flipping” 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 Configuration
For audio to pass to and from the Model
370A requires that several Dante-related
parameters be configured. These configu-
ration 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 www.audinate.com. Versions
of Dante Controller are available to sup-
port 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 (Tx) channels
associated with the Model 370A’s Dante
interface must be assigned to the desired
receiver (Rx) channels. This achieves rout-
ing 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 flow (a group
of output channels) to a receiver flow (a
group of input channels). The number of
transmitter flows associated with an Ultimo
integrated circuit is limited to two. These
can either be unicast, multicast, or a com-
bination of the two. If the Model 370A’s
transmitter channels need to be routed us-
ing more than two flows it’s possible that
an intermediary device, such as the Studio
Technologies Model 5422 Dante Intercom
Audio Engine, can be used to “repeat” the
signals. (Use the Model 5422’s pass-thru
group configuration mode to provide this
resource.)
The two Dante receiver (Rx) channels
associated with the Model 370A’s audio
inputs also need to be routed to the Dante
transmitter (Tx) channels provided 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 clock master for a Dante
network but in most cases it will be con-
figured to “sync” to another device that
is serving as the “grand master” for the
Dante implementation.

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The Model 370A has a default Dante device
name of ST-M370A- followed by a unique
suffix. The suffix identifies the specific
Model 370A that is being configured. The
suffix’s actual alpha and/or numeric charac-
ters relate to the MAC address of the unit’s
Ultimo integrated circuit. The two Dante
transmitter (Tx) channels have default
names of Ch1 and Ch2. The two Dante
receiver (Rx) channels have default names
of Ch1 and Ch2. Using the Dante Control-
ler application the default device name and
channel names can be revised as appropri-
ate for the specific application.
Model 370A Configuration
Many of the Model 370A’s operating param-
eters can be configured to match the needs
of specific applications. The STcontroller
software application is used to observe a
unit’s current configuration and perform any
changes that are required. No DIP switch
settings or other local actions are used to
configure 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
(www. studio-tech.com/stcontroller) and
is compatible with personal computers
running Windows operating systems that
are version 7 and later. STcontroller ver-
sions 2.02.00 and later are required to
fully support the Model 370A. If neces-
sary, download and install STcontroller
onto a designated personal computer. This
personal computer must be on the same
local area network (LAN) and subnet as
the Model 370A unit or units that are to be
configured.
STcontroller allows observation and selec-
tion of functions that include:
• Microphone Input – Electret Power
• Microphone Input – Gain
• Headphone Output Channel Routing
• Sidetone – Level
• Button Operation
• System – Mic Kill
Changes made using STcontroller will be
immediately reflected in the unit’s opera-
tion; 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 flash orange in a dis-
tinctive pattern to indicate that a command
from STcontroller has been received.
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
command to allow easy recognition of a
specific Model 370A unit. Double clicking
on a device name will cause the associated
configuration menu to appear. Review the
current configuration 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 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 termi-
nate on a 5-pin male XLR connector will

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not require microphone power. The on/off
status is displayed by way of a red LED,
labeled MIC POWER, that is located adja-
cent to the headset connector.
Note that the Model 370A cannot supply
P12 or P48 phantom power that may be
required for balanced condenser (capaci-
tor) microphones. This should not pose an
issue as this type of microphone is essen-
tially 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 provid-
ed by electret microphones. As such, the
42 or 48 dB gain settings will probably be
appropriate for them. Electret microphones
often have internal circuitry which provides
a relatively high output level. The 22 and
30 dB gain settings will typically be appro-
priate 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. Set-
ting 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 use-
ful when the Model 370A is going to be
deployed at events where users are not
able to speak at normal levels, e.g., sport-
ing events such as golf tournaments where
“whispering” may be necessary.
Electret microphones typically have a
higher output level due to their internal
preamplifier circuitry. As such, less pream-
plifier 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 visible adjacent to the headset
connector, can act as a guide when setting
the microphone preamplifier gain. Dur-
ing 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 dur-
ing 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 audio input sources (Dante receiver
channels) can be assigned to the head-
phone output channels using the Dante
Controller application. How these two
audio signals are routed to the Model
370A’s headphone output channels can
be configured using this configuration
choice. The three options provide flexibility
in how the audio sources are presented
to the user. When using a stereo (“double
muff”) headset it’s common for the audio
input sources to be routed to both the left
and right channels. But the Model 370A’s
flexibility allows each source to be inde-
pendently configured for sending to the left
only, right only, or both left and right head-
phone channels.
When using a stereo headset sending all
inputs to both channels is often referred to
as a dual-channel mono output. If a mon-
aural (“single muff”) headset is used the
Left configuration option allows the two
input channels to be combined to monau-
ral so that the listener can simultaneously
hear both sources.

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Sidetone – Level
Choices are Off, Low, Medium Low,
Medium, Medium High, and High.
The Model 370A includes a sidetone
function that allows microphone audio
coming from the microphone preampli-
fier to be sent to the both channels of
the headphone output. This serves as a
user confirmation 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 five values.
The correct value is simply the one that
makes the user most comfortable. Side-
tone audio can also be disabled by se-
lecting Off. Selecting Off 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 configuration section allows indepen-
dent selection of how the two talk buttons
will function. When the Push to Talk mode
is selected the operation is self-explanato-
ry. Only when a talk button is pressed and
held will talk audio be sent out its associ-
ated Dante transmitter channel.
When the Latching mode is selected tap-
ping (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.
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 channel.
When the button is released audio will
stop being sent out its associated trans-
mitter 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 lon-
ger be active.
Many applications are best served when
the buttons are configured in the Push to
Talk mode. This ensures that a channel
can’t accidentally be left in its talk active
mode. But there are certainly valid situa-
tions 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 channel.
This can be useful when the audio input
associated with this channel is going to be
monitored but talk audio is not allowed to
“join” this specific intercom channel.
System – Mic Kill
Choices are Off, 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 con-
trol. Specifically, it’s possible to remotely
change all active (on) talk channels to
their off state. This function is sometimes
referred to as a “talk off” function. There
are two means available to remotely dis-
able all active talk channels. The Device ID
method uses the identification command

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generated by the Dante Controller or
STcontroller software applications as a
“trigger” to disable any active talk chan-
nels. The Global Kill Command can be gen-
erated by applications that incorporate the
Studio Technologies’ proprietary method.
This method utilizes sending a data com-
mand over the Ethernet connection. Select
the desired mic kill configuration 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 connection 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 configura-
tion should have been selected to meet
the needs of the specific application. The
Model 370A’s Dante configuration settings
should have been selected using the Dante
Controller software application. In this way
the Model 370A’s two audio output chan-
nels (Dante transmitter channels) and two
audio input channels (Dante receiver chan-
nels) 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 connected. However, it may take
20 to 30 seconds for full operation to com-
mence. Upon initial power up the three
status LEDs located on the bottom panel
below the etherCON RJ45 receptacle will
begin to light as network and Dante con-
nections 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 ap-
plication firmware (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 receptacle on the Model
370A’s bottom panel. The LINK ACT LED
will light green whenever an active con-
nection to a 100 Mb/s Ethernet network
has been established. It will flash in re-
sponse 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 indi-
cate 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 flash green
when this specific Model 370A is serving
as the clock master for the network. It’s
possible that up to 30 seconds may be
required for the SYNC LED to reach its
final state.

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Compressor Active LED
A yellow LED indicator is located on the
bottom panel adjacent to the headset
connector. Labeled COMP, the LED dis-
plays the status of the microphone audio
compressor function. It will light whenever
the input level from the microphone, along
with the configured preamplifier gain, is
such that the dynamic range of the talk
signal is being controlled. It’s perfectly ac-
ceptable for this LED to light intermittently
whenever a user is talking at a normal
voice level into the associated micro-
phone. 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 ben-
eficial. 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”), locat-
ed 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. Depend-
ing on the configuration 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 protec-
tion from an unwanted change is desired.
Users should find the headphone output
audio quality 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/off sta-
tus 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-
figuration of the unit. Each button can be
configured independently.
Push to Talk
When a button has been configured 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 output
(transmitter) 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 (“tapping”) the button will cause
the function to change states; off-to-on or
on-to-off. Whenever the talk function is ac-
tive 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 configured for the
Push to Talk/Tap to Latch mode operation
is a bit different and certainly more flex-
ible. Press and hold the button to activate

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the talk function. When released the talk
function will turn off. Momentarily pressing
(“tapping”) the button will cause the func-
tion to change states; off-to-on or on-to-off.
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 configured to the Disabled
mode will never allow talk audio to be sent
to the associated Dante audio output chan-
nel. But to provide “feedback” that the but-
ton has been pressed the button’s green
LED will flash rapidly three times. This says,
in effect, “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 func-
tion 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 confidence signal that they
are actively talking to other intercom us-
ers. Sidetone audio will always be sent to
both the left and right headphone channels
and is not a configurable 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 in-
tended to indicate to the user which Dante
audio output (transmitter) channel or chan-
nels are actively sending audio.
The exact sidetone level is configured
from among five values within the STcon-
troller 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
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 visu-
ally. 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 chan-
nels 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 con-
fused with a call signal. Digital filters 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 filtering is also
performed on the audio input (Dante re-
ceiver) signals before they are sent to the

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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 en-
able either or both of the talk buttons and
simultaneously press and hold the call
button. When call sending is active the or-
ange 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
flash. 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 chan-
nel receives a call signal (20 kHz audio
tone) the orange LED on its companion
talk button will first flash and then light
continually. If a call signal is present on
both audio input channels then the orange
LEDs on both talk buttons will first flash
then remain lit. When receiving a call sig-
nal 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 vener-
able RTS BP-325. When interconnecting
Model 370A and BP-325 units using an
appropriate Dante-enabled interface, such
as the Studio Technologies’ Model 45DR
Intercom Interface, call signaling is fully
compatible. Compatibility with the Clear-
Com method of call functionality is also
possible by using the Model 45DC Inter-
com Interface. (It converts the DC call sig-
nal associated with pin 3 of a Clear-Com
party-line circuit to a 20 kHz tone.) Also,
devices such as the Studio Technologies
Model 44D Audio Interface will send and
receive 20 kHz signals that are be com-
patible with the Model 370A. The Model
44D 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 44D will be monitored for the pres-
ence of 20 kHz call signals. If call signals
are detected the GPO (general-purpose
output) signals will activate.
How to Identify a Specific
Model 370A
The Dante Controller software applica-
tion offers an Identify command that can
be used to help locate a specific Model
370A. When Identify is selected it will send
a command to a single Model 370A unit.
On that specific 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 receptacle on the bot-
tom panel, will slowly flash green. After a
few seconds the LED identification pattern
will cease and normal Model 370A button
LED and Dante status LED operation will
resume.
If configured, the Identify command can
also cause the mic kill function to activate.
For details please refer to the next para-
graph of this guide.
Mic Kill Function
The Model 370A includes a mic kill func-
tion, allowing talk buttons that have been
placed in their enabled (on) state to be
remotely changed to their disabled (off)

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MODEL 370A
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state. This allows one or both talk chan-
nels 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 us-
ers to enable a talk channel and then go
“off 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. Having the ability
to disable this talk channel can be very
useful.
A configurable 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 specific
Model 370A is identified using the Iden-
tify 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 in-
terface will attempt to automatically obtain
an IP address and associated settings
using the DHCP (Dynamic Host Configu-
ration Protocol). If a DHCP server is not
detected an IP address will automatically
be assigned 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 intercon-
nected using an RJ45 patch cable will,
in most cases, correctly acquire IP ad-
dresses and be able to communicate with
each other.
An exception does arise when trying to
directly interconnect 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 an-
other 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 flow.
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 ap-
plication would use two Model 370A units
without a PoE-enabled Ethernet switch
being present.
Using the Dante Controller software ap-
plication the Model 370A’s IP address
and related network parameters can be
manually set for a fixed (static) configura-
tion. While this is a more-involved process
than simply letting DHCP or link-local
automatically assign an address, if fixed
addressing is necessary then this capabil-
ity is available. But in this case it’s highly

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recommended that each unit be physically
marked, e.g., directly using a permanent
marker or “console tape,” with its specific
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) networking 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 in-
cludes MAC addresses and corresponding
IP addresses. The simplest means of identi-
fying 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 per-
formance a network that supports VoIP
Quality-of-service (QoS) capability is rec-
ommended. This can be implemented on
virtually all contemporary managed Ether-
net switches. There are even specialized
switches that are optimized for entertain-
ment-associated applications. Refer to
the Audinate website (www.audinate.com)
for details on optimizing networks for Dante
applications. Also, be certain to disable
Energy-Efficient Ethernet (EEE) support on
all Ethernet switch ports that are associated
with Dante devices. Some implementations
of EEE can incorrectly interpret that a con-
nected device is not present and prevent
proper Dante operation.
Application Firmware Version
Display
There are two ways in which the version
number of the Model 370A’s application
firmware (embedded software) can be
identified. 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 application. Either
method may prove to be useful when work-
ing with factory personnel on application
support and troubleshooting.
As part of the Model 370A’s power-up
sequence the unit’s application firmware
(embedded software) version number can
be displayed. Before connecting the PoE-
enabled Ethernet cable, press and hold
the call button. Then connect the Ether-
net cable. Upon application of PoE power
the Model 370A will go through its normal
power-up sequences followed by a display
of the firmware version. The LED associ-
ated with the channel 1 talk button will
“flash” to display the major version number.
Then the LED associated with the channel
2 talk button will “flash” 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 firmware display, if the channel
1 talk button “flashes” once followed by
the channel 2 talk button “flashing” two
times this would indicate that application
firmware version 1.2 was present in the
Model 370A.
A selection in the STcontroller software
application allows the Model 370A’s ap-
plication firmware version to be identified.
Connect the Model 370A unit to the net-
work and let it connect and start to func-

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MODEL 370A
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tion. Then, after starting STcontroller, review
the list of identified devices and select the
specific Model 370A that interests you. Then
select Version under the Device tab. A page
will then display that will provide lots of use-
ful information. This includes the application
firmware version and well as details on the
firmware present in the Ultimo integrated
circuit.
Application Firmware Update
Procedure
It’s possible that updated versions of the ap-
plication firmware (embedded software) that
is utilized by the Model 370A’s processor
(microcontroller or MCU) integrated circuit
will be released to add features or to cor-
rect issues. Refer to the Studio Technologies
website for the latest application firmware
file. The unit has the ability to load a revised
file into the MCU’s non-volatile flash memory
by way of a USB interface. The Model 370A
implements a USB host function that directly
supports connection of a USB flash drive.
The Model 370A’s MCU updates its applica-
tion firmware using a file named M370A.bin.
The update process begins by preparing
a USB flash drive. The flash drive doesn’t
have to be empty (blank) but must be in the
personal-computer-standard FAT32 format.
Save the new application firmware file in the
root directory with a name of M370A.bin.
Studio Technologies will supply the applica-
tion firmware file inside a .zip archive file.
While the application firmware file inside
of the zip file will adhere to the naming
convention required by the Model 370A,
the name of the zip file itself will include
the file’s version number. For example, a file
named M370Av1r2MCU.zip would indicate
that version 1.2 of the application firmware
(M370A.bin) is contained within this zip file.
Once the USB flash drive is inserted into
the USB interface, located on the main cir-
cuit board under the cover, the unit must be
powered off and again powered on. At this
point the file will automatically be loaded
into the processor’s flash memory. The pre-
cise steps required will be highlighted in the
next paragraphs of this guide.
To update the application firmware file
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 off.
3. Locate the USB connector on the main
circuit board. It’s near the call button.
Insert the prepared USB flash drive
into it.
4. Apply power to the Model 370A by con-
necting to a Power-over-Ethernet (PoE)
Ethernet source.
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 flash slowly in alternating col-
ors. Once the entire process is over,
taking approximately 10 seconds, the
Model 370A will restart using the newly-
saved application firmware.

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6. At this time the Model 370A is operat-
ing under the newly-saved application
firmware and the USB flash drive can
be removed. But to be conservative,
remove PoE power first and then re-
move the USB flash drive.
7. Confirm that the desired application
firmware version 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 firmware
version number by first observing the
channel 1 talk button’s LED and then
observing the channel 2 talk button’s
LED. Alternately, the STcontroller
software application can be used to
identify the application firmware ver-
sion 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 flash drive
doesn’t have the correct file (M370A.bin)
in the root folder no harm will occur. If the
correct file is not present upon power up
the call button’s LED will flash on and off
rapidly for a few seconds to indicate this
error condition and then normal operation
using the unit’s existing application firm-
ware will begin.
Ultimo Firmware Update
As previously discussed in this guide,
the Model 370A implements Dante con-
nectivity 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 firmware version.
(Use the Version selection under the
Device tab.) The Ultimo firmware can
be updated by way of the Model 370A’s
Ethernet connection. The latest Ultimo firm-
ware file is available on the Studio Technol-
ogies website. The Dante Firmware Update
Manager (FUM) application program can
be used to install the Ultimo firmware. The
Dante Controller software application also
includes an automated method of updating
Ultimo firmware. It offers a much simpler
method of keeping the Ultimo firmware
current.
Model 370A versus Model 370
Some users may be interested in the dif-
ferences between the original Model 370
Intercom Beltpack and the newer Model
370A that is 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 applica-
tion firmware (embedded software)
and Ultimo firmware to be remotely
identified.
• 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.