Studio Technologies 370 User manual

Copyright © 2017 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50621-0517, Issue 3
This User Guide is applicable for serial numbers:
• M370-00251-02000 with application firmware 2.2 and later
and Dante firmware 2.0 (Ultimo 3.10.1.12) and later
• M370-02001 and later with application firmware 2.2 and later
and Dante firmware 3.0 (UltimoX2 3.10.3.1) and later
Model 370 Intercom Beltpack
User Guide
Issue 3, May 2017

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Model 370 User Guide Issue 3, May 2017
Studio Technologies, Inc. Page 3
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 7
Operation ...................................................................... 12
Technical Notes ............................................................. 15
Specifications ................................................................ 19

Issue 3, May 2017 Model 370 User Guide
Page 4 Studio Technologies, Inc.
Revision History
Issue 3, May 2017:
1. Documents revised call light function. Documents added action when identify command
is active.
Issue 2, August 2016:
1. Released strictly for incorporating typographical corrections and enhanced
explanations.
Issue 1, April 2016:
1. Initial release.

Model 370 User Guide Issue 3, May 2017
Studio Technologies, Inc. Page 5
Introduction
The Model 370 Intercom Beltpack starts
with the features required of traditional
broadcast 2-channel party-line (PL) inter-
com user devices and adds the advanced
performance and capabilities that Dante
audio-over-Ethernet provides. Over a stan-
dard IP network, multiple Model 370 units
can be used in PL intercom applications
with help from an external Dante-enabled
audio matrix. Or, units can be used “point-
to-point” or directly interfaced with ports
on compatible matrix intercom systems.
Only a single Power-over-Ethernet (PoE)
connection is required for operation. Key
user features can be easily configured
including preamplifier gain, talk button
operation, and headphone signal routing.
User features include integrated sidetone,
remote microphone off, and call alerting.
This capability, along with the great audio
quality provided by the digital audio signal
path, offers a superior user experience.
Set up and configuration of the 2-channel
Model 370 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 connec-
tion provides both power and bidirectional
digital audio. A broadcast or intercom-style
stereo or monaural headset with a dynamic
microphone interfaces to the unit using a
5-pin XLR connector. Five DIP switches
are used to establish the unit’s operating
parameters. Two “push-in/push-out” rotary
level controls make it easy to set the head-
phone output volume as well as maintain-
ing the desired settings. The Model 370’s
enclosure is made from an aluminum alloy
which offers both light weight and rugged-
ness. A stainless steel “belt clip,” located
on the back of the unit, allows direct attach-
ment to a user’s clothing.
The audio quality of the Model 370’s two
audio channels is excellent, with low distor-
tion, low noise, and high headroom. Careful
circuit design and rugged components en-
sure long, reliable operation. A wide range
of applications can be supported, including
TV, radio, and streaming broadcast events,
corporate and government AV installations,
and post-production facilities.
Dante Audio-over-Ethernet
Audio data is sent to and received from
the Model 370 using the Dante audio-over-
Ethernet media networking technology.
As a Dante-compliant device, the Model
370’s two output (Dante transmitter) and
two input (Dante receiver) audio channels
can be assigned to other devices (routed)
using the Dante Controller software appli-
cation. The Dante transmitter and receiver
channels are limited to supporting four
Figure 1. Model 370 Intercom Beltpack top and bottom views

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Dante flows, two in each direction. The
digital audio’s bit depth is 24 with a sam-
pling rate of 48 kHz. Two bi-color LEDs
provide an indication of the Dante connec-
tion status. The Dante Controller’s identify
command takes on a unique role with the
Model 370. Not only will it cause the talk
button LEDs to light in a unique highly vis-
ible sequence, it will also turn off any active
talk channels.
Audio Quality
The Model 370’s completely “pro”
performance really bucks the reputation
of “intercom audio.” A low-noise, wide
dynamic-range microphone preamplifier
and associated voltage-controller-amplifier
(VCA) dynamics controller (compressor)
ensures that input audio quality is pre-
served while minimizing the chance
of signal overload. The output of the micro-
phone preamp and compressor is routed
to an analog-to-digital conversion (ADC)
section that supports a sampling rate of
48 kHz with a bit depth of up to 24. The au-
dio signal, now in the digital domain, routes
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 the Dante
receiver channels and pass into the Model
370’s processor. The sampling rate is
48 kHz with a bit depth of up to 24. Chan-
nel routing, headphone level control, and
sidetone creation are performed in the digi-
tal domain. This provides flexibility, allows
precise control, and keeps the three user
level potentiometers (channel 1, channel 2,
and sidetone) from having to directly han-
dle analog audio signals. The two audio
channels destined for the phones outputs
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 370 users to
send and receive channel-specific visual
alert signals. Pressing the dedicated call
button on the top of a unit is all that’s re-
quired to signal other users that attention
is requested. Using 20 kHz tones, the call
signals are sent within the audio chan-
nels (“in band”) allowing interoperability
between multiple Model 370 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.
Configuration Flexibility
A highlight of the Model 370 is its ability to
be easily configured to the meet the needs
of specific users and applications. Five
DIP switches allow control of the micro-
phone preamplifier gain, talk button opera-
tion, and audio routing to the headphone
outputs. The gain of the microphone
preamplifier can be selected from nomi-
nally 40 or 46 dB. This allows compatibility
with dynamic microphones that are part
of many industry-standard broadcast and
intercom headsets. The two pushbutton
switches that control the talk audio on/off
status can be individually configured for
push to talk or push to talk/tap to latch
operation. Two audio channels arrive via
Dante and are destined for the headphone
outputs. Each input can be independently
routed to one or both audio outputs. This

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Studio Technologies, Inc. Page 7
allows a variety of listening environments
to be created, including dual-channel
monaural.
Ethernet Data and PoE
The Model 370 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 connector. While
compatible with standard RJ45 plugs,
etherCON allows a ruggedized and lock-
ing interconnection for harsh or high-
reliability environments. An LED displays
the status of the network connection.
The Model 370’s operating power is pro-
vided by way of the Ethernet interface us-
ing the 802.3af Power-over-Ethernet (PoE)
standard. This allows fast and efficient
interconnection with the associated data
network. To support PoE power man-
agement, the Model 370’s PoE interface
reports to the power sourcing equipment
(PSE) that it’s a class 1 (very low power)
device. If a PoE-enabled Ethernet port
can’t be provided by the associated Ether-
net switch a low-cost PoE midspan power
injector can be utilized.
Future Capabilities and
Firmware Updating
The Model 370 was designed so 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.
To implement the Dante interface the
Model 370 uses Audinate’s Ultimo™
integrated circuit. The firmware in this
integrated circuit can be updated via the
Ethernet connection, helping to ensure
that its capabilities remain up to date.
Getting Started
What’s Included
Included in the shipping carton are a
Model 370 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. Should
a PoE midspan power injector be required
it must be purchased separately.
Connections
In this section signal interconnections
will be made using the two connectors
located on the bottom of the Model 370.
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- or single-earpiece headset (stereo
or monaural) 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 370 operation. This one
connection will provide both the Ethernet
data interface and power for the Model
370’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 370 supports Ether-
net switch power management, enumerat-
ing itself as a PoE class 1 device.

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The Ethernet connection is made by way
of a Neutrik etherCON protected RJ45
connector that is located on the bot-
tom panel of the Model 370. This allows
connection by way of a cable-mounted
etherCON connector or a standard RJ45
plug. The Model 370’s Ethernet interface
supports auto MDI/MDI-X so that a “cross-
over” or “reversing” cable should not be
required.
Ethernet Connection without PoE
As previously discussed in this guide,
the Model 370 was designed such that
the Ethernet connection will provide both
data and Power-over-Ethernet (PoE)
power. There may be situations where the
associated Ethernet switch does not pro-
vide PoE power. In such cases an external
PoE midspan power injector can be used.
If the selected midspan power injector is
802.3af-compatible it should function cor-
rectly. Midspan units are available from a
variety of sources, including many online
retailers.
Headset Connection
The Model 370 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
intended for use with unbalanced dynamic
microphones. Balanced microphones
should, in most cases, also function cor-
rectly if the signal – (low) is connected to
Model 370’s mic in –/shield connection.
No support is provided for microphones
that require low-voltage “eletret,” P12
phantom, or P48 phantom powering.
To allow users of stereo (dual-earpiece
or “double-muff”) headsets to hear a
monaural version of the two output chan-
nels does not require special wiring of the
5-pin male XLR mating connector. The
headset’s left phones channel should
always be wired to pin 4 and the right
phones channel to pin 5. Configuration
choices, discussed later in this guide, can
then be used to create the desired mon-
aural output. It’s important not to connect
together (short) pins 4 and 5 of the Model
370’s headset connector as damage to
the Model 370’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. The configura-
tion switches, discussed later in this guide,
can be used to create a monaural output.
(Technically this can send audio to both
pins 4 and 5 of the Model 370’s headset
connector but the headset will only con-
nect to pin 4.)
It’s possible that some Beyerdynamic in-
terconnecting cable assemblies terminate
their 5-pin male XLR connector with their
earpiece’s left channel on pin 5 and right
channel on pin 4. This is opposite from
Figure 2. Headset connection pinout chart

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Studio Technologies, Inc. Page 9
what the Model 370 requires. As such,
“flipping” pins 4 and 5 in the headset’s
5-pin male XLR connector may be required
so that the left and right channels from the
Model 370 match correctly.
Dante Configuration
For audio to pass to and from the Model
370 requires that several Dante-related
parameters be configured. These configu-
ration settings will be stored in non-volatile
memory within the Model 370’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 support
Windows® and OS X® operating systems.
The Model 370 uses the Ultimo 2x2 chan-
nels (2-input/2-output) integrated circuit to
implement the Dante architecture.
The two Dante transmitter (Tx) channels
associated with the Model 370’s Dante
interface must be assigned to the desired
receiver channels. This achieves rout-
ing the Model 370’s two talk output audio
channels to the device (or devices) that will
be “listening” to them. Within Dante Con-
troller a “subscription” is the term used for
routing a transmitter flow (a group of out-
put 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, mul-
ticast, or a combination of the two. If the
Model 370’s transmitter channels need to
be routed to more than two flows it’s pos-
sible that an intermediary device, such as a
rack-mounted digital signal processor unit
with more available flows, can be used to
“repeat” the signals.
The two Dante receiver (Rx) channels as-
sociated with the Model 370’s audio inputs
also need to be routed to the desired Dante
transmitter channels. These two audio sig-
nals will be sent to the Model 370’s head-
phone outputs.
The Model 370 supports an audio sample
rate of 48 kHz with a limited selection of
pull-up/pull-down values available. In most
cases the default will be used and a pull-up
or pull-down rate will not be selected. The
Model 370 can serve as the clock master
for a Dante network but in most cases it will
be configured to “sync” to another device.
The Model 370 has a default Dante device
name of ST-M370 and a unique suffix. The
suffix identifies the specific Model 370 that
is being configured. The suffix’s actual al-
pha and/or numeric characters 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
Dante Controller the default device name
and channel names can
be revised as appropriate for the specific
application.
Model 370 Configuration
Five DIP switches are used to select the
mic preamplifier gain and how the user
controls on the Model 370 will function.
These configuration choices allow the
performance of the unit to be optimized for
specific applications and user preferences.
The switches are accessible from the back
of the unit’s enclosure, through a small
opening that is located under the top of the
belt clip. To access the switches requires
that the belt clip be rotated. Normally the
belt clip is secured to the back using one

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Page 10 Studio Technologies, Inc.
rivet (non-removable) and one machine
screw that has a thread pitch of 6-32. To
allow the belt clip to rotate, remove the
machine screw using a #1 Phillips-head
screwdriver. The belt clip should now be
able to be easily rotated in either direc-
tion. Save the screw so that it can be
re-installed once the desired configura-
tion choices have been made. Note that
the threaded fastener within the back of
the Model 370’s chassis has an internal
locking mechanism (a plastic bushing)
that prevents the belt clip’s 6-32 machine
screw from vibrating loose. So no addi-
tional method of thread locking, such as
a lock washer or chemical compound, is
necessary.
The five switches provide a nice set of
configuration choices. One allows the
gain of the microphone preamplifier to
be adjusted. Two of the switches are
used to select how the talk buttons func-
tion. And the last two switches select how
the input audio signals are routed to the
headphone outputs. The five switches are
connected to the Model 370’s logic circuit-
ry which responds to changes by way of
the application firmware; no audio passes
directly through the switches. Changes
made to any of the switches will immedi-
ately be reflected in the unit’s operation.
A power cycle is not required for con-
figuration changes to be recognized and
implemented.
Microphone Preamp Gain
Switch SW1 allows the gain of the micro-
phone preamplifier to be selected. When
SW1 is in its down (off) position 40 dB of
gain is selected. This will be appropriate
for most applications. (Technically this
gain is approximately equal to the gain
provided within an RTS® BP-325 analog
party-line beltpack.) Place SW1 to its up
(on) position to select the 46 dB gain set-
ting. This additional 6 dB of gain may be
helpful in some applications, such as with
headsets that have a low microphone out-
put level. The higher gain setting may also
be useful when the Model 370 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.
The compressor active LED, visible on
the bottom of the Model 370 adjacent to
the headset connector, can act as a guide
when setting the preamp gain. During
normal talk operation the compressor
active LED should light intermittently. If it
rarely lights and the gain is set to 40 dB, it
might be a good idea to change to setting
to 46 dB. If the LED is lit fully during nor-
mal talking and the gain is set for 46 dB,
changing it to the 40 dB setting might be
warranted. There’s no “hard and fast” rule
about what gain setting is appropriate.
But unless otherwise indicated, 40 dB
is typically a good choice.
Talk Button Modes
On the Model 370’s top panel are two
pushbutton switches that allow the user
to control the on/off status of the headset
microphone audio that’s sent to the two
audio output (Dante transmitter) channels.
Configuration switches SW2 and SW3
allow the buttons’ operating modes to be
Figure 3. Microphone preamp gain
configuration switch

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Studio Technologies, Inc. Page 11
independently configured. The two operat-
ing choices are push to talk and push to
talk/tap to latch. SW2 is used to select the
operating mode for the talk button associ-
ated with channel 1. SW3 is used to select
the operating mode for the talk button
associated with channel 2. Many applica-
tions are best served when the buttons are
configured for push to talk operation. This
ensures that a channel won’t accidentally
be left in the talk mode. But there certainly
are valid situations where the push to talk/
tap to latch setting will prove to be very
useful.
Model 370’s flexibility allows either or both
sources to be sent to both the left and right
outputs thus creating a monaural listening
environment. When using a stereo headset
this is often referred to as a dual-channel
mono output. If a monaural (“single-muff”)
headset is used these configuration op-
tions allow the two input channels to be
combined to monaural so that the listener
can hear both input sources.
When SW4 is in its down (off) position au-
dio from input channel 1 will be sent to the
left channel (pin 4) of the headset connec-
tor. When SW4 is in its up (on) position the
audio is sent to both the left channel (pin 4)
and the right channel (pin 5) of the headset
connector.
When SW5 is in its down (off) position
audio from input channel 2 will be sent
to the right channel (pin 5) of the headset
connector. When SW5 is in its up (on)
position the audio is sent to both the left
channel (pin 4) and the right channel
(pin 5) of the headset connector.
Figure 4. Channel 1 and channel 2 talk button
mode configuration switches
Figure 5. Channel 1 and channel 2 headphone
audio routing mode configuration switches
Headphone Audio Routing Modes
How the Model 370’s two audio input
(Dante receiver) channels are routed to
the headphone output channels can be
configured using switches SW4 and SW5.
The choices provide flexibility in how the
audio sources are presented to the user.
When using a stereo (“double-muff”)
headset it’s common for the two audio
input sources to be independently routed
to the left and right channels. But the

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Operation
At this point Model 370 operation should
be taking place. An Ethernet connection
with Power-over-Ethernet (PoE) capabil-
ity should have been made. Alternately, a
midspan power injector, in “series” with
the Ethernet connection, should have
been put into place. A headset terminated
on a 5-pin male XLR connector should be
plugged into the headset connector.
The Model 370’s Dante configuration set-
tings should have been selected using
the Dante Controller software application.
In this way the two audio output (Dante
transmitter) channels and two audio input
(Dante receiver) channels should have
been routed to the Dante receivers and
transmitters on associated equipment.
The Model 370’s five configuration switch-
es should have been used to select the
desired operating characteristics.
Initial Operation
The Model 370 will begin to function as
soon as a Power-over-Ethernet (PoE) pow-
er source is connected. However, it may
take 20 seconds or longer for full opera-
tion to commence. Upon initial power up
the three status LEDs located on the bot-
tom panel below the etherCON RJ45 jack
will begin to light as network and Dante
connections are established. The three
pushbutton switches on the top panel will
light in a test sequence to indicate that
the main operating firmware (embedded
software) has started. Once the entire
sequence has completed and the Dante
connection has been established full op-
eration will begin.
Ethernet and Dante Status
LEDs
Three status LEDs are located below the
etherCON RJ45 connector on the Model
370’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 370 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 370 is
not synchronized with a Dante network. It
will light solid green when the Model 370
is synchronized with a Dante network and
an external clock source (timing reference)
is being received. It will slowly flash green
when the Model 370 is part of a Dante
network and is serving as a clock master.
It’s possible that up to 20 seconds may
be required for the SYNC LED to reach
its final state.
How to Identify a Specific
Model 370/Remote Talk
Off Function
The Dante Controller software applica-
tion offers an identify command that can
be used to help locate a specific Model
370. When identify is selected it will send
a command to a single Model 370 unit.
On that specific unit the three pushbutton
LEDs (two talk on/off and call) will light
in a unique pattern. In addition, the SYS
and SYNC status LEDs, located directly
below the etherCON RJ45 connector on

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Studio Technologies, Inc. Page 13
the bottom panel, will slowly flash green.
After a few seconds the LED identification
patterns will cease and normal Model 370
button LED and Dante SYS and SYNC
status LED operation will resume.
The identify command also causes a talk
off (“mic kill”) function to activate. If either
or both talk on/off buttons are configured
to the push to talk/tap to latch mode, and
they are latched on, the identify command
will cause them to latch off. This allows
talk channels on a specific Model 370
that have been accidentally enabled to
be remotely turned off. A subtle but inter-
esting action will also occur if the identify
command is received when the Model 370
is in a specific configuration and talk op-
eration is active. If either or both of the talk
buttons have been configured for push to
talk operation and either or both buttons
are pressed to enable talk, when the iden-
tify command is received the microphone
audio will be muted for approximately one
second. This is implemented to allow tech-
nical personnel to use the identify com-
mand to locate a specific Model 370 that
might have had one or both of its buttons
accidentally activated.
For example, if a Model 370 was removed
from a user’s belt or other clothing and
then pushed into the corner of a table or
studio set it’s possible that either or both
talk buttons could become depressed.
The identify command would cause the
audio path on that specific unit to be
momentarily disabled, providing an aural
“clue” as to which unit is in an unwanted
state and helping guide personnel to iden-
tify its location. This feature only disturbs
the audio path for a brief interval, ensuring
that a valid talk condition won’t be unduly
impacted.
Listen Level
Two rotary level controls (“pots”), located
on the Model 370’s top panel, allow ad-
justment of the level of the two audio input
signals as they are sent to the headphone
outputs. Depending on the configuration
of the unit, audio input 1 can be sent to
the left headphone output or to both the
left and right headphone outputs; audio
input 2 can be sent to the right head-
phone output or to both the left and right
headphone outputs. The pots are “push-
in/push-out” type which allows the associ-
ated knobs to be in their “out” positions to
be adjusted and their “in” positions when
protection from changes is desired.
The headphone output audio quality
should be excellent, with high maximum
output level and low distortion. High-
frequency audio content is limited above
10 kHz, preventing unwanted signals from
reaching the transducers of the associated
headset. Analog audio signals do not pass
directly through the rotary level controls.
The position of the pots is recognized by
the Model 370’s processor which then ad-
justs the signal level in 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
channels, or the status of the call function,
does not impact the headphone outputs.
They are independent functions.
Compressor Active LED
A yellow LED indicator is located on the
bottom panel adjacent to the headset con-
nector. Labeled COMP, the LED displays
the status of the microphone audio com-
pressor function. It will light whenever the
input level from the microphone is such
that the dynamic range of the talk signal

Issue 3, May 2017 Model 370 User Guide
Page 14 Studio Technologies, Inc.
is being controlled. It’s perfectly accept-
able for the LED to light intermittently while
a user is talking in a normal voice level
into the microphone. But if the COMP
LED lights solid while a user is talking at
a normal voice level and the mic preamp
gain is set for 46 dB, this will typically in-
dicate that the mic gain setting should be
changed to 40 dB. Conversely, if the LED
almost never lights when normal talking
is taking place and the mic preamp gain
is set for 40 dB, it’s possible that chang-
ing the gain to 46 dB would be beneficial.
The compressor active LED will function
whether or not either or both of the talk
channels are active.
Talk Buttons
Two pushbutton switches are associated
with the Model 370’s audio output chan-
nels. How they function will depend on
the configuration of the unit. Each button
can be configured independently. When a
button has been set for 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 audio output channel. The
button’s green LED will light to indicate
that the output is active. If the button has
been configured for the push to talk/tap to
latch mode operation is a bit different and
certainly more flexible. Press and hold the
button to activate the talk function. When
released the talk function will turn off. Mo-
mentarily pressing (“tapping”) the button
will cause the function to changes states;
off-to-on or on-to-off. Whenever the output
is active the green LED will light.
Sidetone Function
The Model 370 includes a sidetone func-
tion that sends microphone audio to both
the left and right headphone outputs when-
ever either or both of the talk functions are
active. The audio quality should be excel-
lent and will provide the user with a confi-
dence signal that they are actively talking
to other intercom users. Sidetone audio is
always sent to both headphone channels,
even if only talk channel 1 or talk channel
2 is active. This is because the function is
trying to simulate what a user would hear
if they didn’t have a headset covering their
ears. It is not intended to indicate to the
user which output channel is active.
The level of the sidetone audio being sent
to the left and right headphone channels
is adjusted using the rotary level control
(“pot”) located on the bottom of the unit.
A small straight blade screwdriver (e.g.,
a “greenie”) can be used to adjust the pot.
Although with some practice one’s thumb
and index finger can also be effective. Typi-
cally the exact sidetone level is not criti-
cal and most users will not be concerned
about changing it. But setting sidetone to
a reasonable level 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. The
two level controls on the top panel do not
impact the sidetone level. Audio does not
pass directly through the sidetone pot but
instead is used by the Model 370’s proces-
sor to control the level in the digital audio
domain.
Call Function
An integrated call function allows Model
370 users, and users of compatible equip-
ment, to signal to each other visually. Indi-
vidual call functions are provided for each
of the two talk channels. Either or both can
have the call function active at any one

Model 370 User Guide Issue 3, May 2017
Studio Technologies, Inc. Page 15
time. Technically call is achieved by send-
ing a 20 kHz audio tone on the desired au-
dio output channel. This signal is summed
(mixed) with normal talk audio. The Model
370’s two audio input channels continually
monitor for the presence of 20 kHz. A call
signal is recognized on a channel 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 talk signal. Digital filters within
the Model 370’s processor integrated
circuit limit the high frequency response
of the audio signals to about 10 kHz in
both the input and output signal paths.
This helps to ensure that false call detec-
tion won’t take place as well as limiting the
chance of causing issues in events where
headphone extended high-frequency
response is possible, e.g., dog shows or
other animal events.
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 or turn the
call function(s) off and sending of the call
signal will cease. As expected, pressing
the call button when neither talk channel
is active will result in nothing occurring.
Whenever a Model 370 audio input chan-
nel receives a call signal (20 kHz audio
tone) the orange LED on its companion
button will first flash and then light contin-
ually. 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 channels the orange
LED associated with the call button will
not light.
By using a 20 kHz tone the Model 370
is compatible with legacy intercom
equipment, including the venerable RTS
BP-325. When interconnecting Model 370
and BP-325 units using an appropriate
Dante-enabled interface, such as the
Studio Technologies’ Model 45DR, call
signaling is fully compatible. Compatibility
with the Clear-Com method of call func-
tionality is possible by using the Model
45DC party-line interface. Also, devices
such as the Studio Technologies’ Model
44D Audio Interface product will send and
receive 20 kHz signals that will be compat-
ible. The Model 44D refers to these signals
as GPI (general purpose input) and GPO
(general purpose output) but the actual
signaling utilizes 20 kHz tones which are
transported “in band” via the Dante audio
paths.
Technical Notes
IP Address Assignment
By default the Model 370’s Ethernet inter-
face will attempt to automatically obtain
an IP address and associated settings
using DHCP (Dynamic Host Configura-
tion 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 (PIPPA). Link-local will assign an IP
address in the IPv4 range of 169.254.0.1
to 169.254.255.254. In this way multiple

Issue 3, May 2017 Model 370 User Guide
Page 16 Studio Technologies, Inc.
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 cord will, in most cases, cor-
rectly acquire IP addresses and be able to
communicate and transport audio. An ex-
ception does arise when trying to directly
interconnect two Dante-enabled devices
that use the Ultimo Dante implementation,
such as two Model 370 units. An Ethernet
switch is required to provide the Ethernet
ports to correctly interconnect two Ultimo-
based devices directly with each other.
(The technical reason relates to the need
for the slight latency provided by an Ether-
net switch.)
Using the Dante Controller software appli-
cation the Model 370’s IP address and re-
lated network parameters can be set for a
fixed (“static”) configuration. While this is a
more involved process than simply letting
DHCP or link-local “do their thing,” if fixed
addressing is necessary then that capabil-
ity is available. But 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 specific
IP address. If knowledge of a Model 370’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 includes MAC addresses and cor-
responding IP addresses. The simplest
means of identifying an unknown IP ad-
dress is to create a “mini” LAN with a per-
sonal computer connected directly to the
Model 370. 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
QoS capability is recommended. This can
typically be implemented on virtually all
contemporary managed Ethernet switches.
There are even specialized switches that
are optimized for entertainment-associated
applications. Refer to the Audinate website
(www.audinate.com) for details on optimiz-
ing networks for Dante applications.
Application Firmware Version
Display
As part of the Model 370’s power-up se-
quence the unit’s application firmware
version number can be displayed. This is
useful when working with factory personnel
on application support and troubleshoot-
ing. Before connecting the PoE Ethernet
cable, press and hold the call button. Then
connect the Ethernet cable. Upon applica-
tion of power the Model 370 will go through
its normal power-up sequences followed
by a display of the firmware version. The
LED associated with the channel 1 talk but-
ton 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 ver-
sion number has been displayed the call
button can be released. As an example
of what would be a typical firmware dis-
play, if the channel 1 talk button “flashed”

Model 370 User Guide Issue 3, May 2017
Studio Technologies, Inc. Page 17
twice followed by the channel 2 talk button
“flashing” once this would indicate that
application firmware version 2.1 was
present in the Model 370.
Application Firmware Update
Procedure
It’s possible that updated versions of the
application firmware (embedded software)
that is utilized by the Model 370’s proces-
sor (microcontroller or MCU) integrated
circuit will be released to add features or
correct issues. Refer to the Studio Tech-
nologies website for the latest application
firmware file. The unit has the ability to load
a revised file into the MCU’s non-volatile
memory by way of a USB interface. The
Model 370 implements a USB host function
that directly supports connection of a USB
flash drive. The Model 370’s MCU updates
its firmware using a file named m370.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 firmware file in the
root directory with a name of m370.bin.
Studio Technologies will supply the ap-
plication firmware file inside a .zip archive
file. While the firmware file inside of the zip
file will adhere to the naming convention
required by the Model 370, the name of
the zip file itself will include the file’s ver-
sion number. For example, a file named
m370v2r1MCU.zip would indicate that
version 2.1 of the application firmware
(m370.bin) is contained within this zip file.
Once the USB flash drive is inserted into
the USB interface, located on the main
circuit board under the cover, the unit
must be powered off and again powered
on. At this point the file will automatically
load. The precise steps required will be
highlighted in the next paragraphs of this
guide. After the firmware has been up-
dated the LEDs associated with the talk
buttons should be used to confirm that the
desired application firmware version has
been successfully installed.
To install the application firmware file fol-
low these steps:
1. Disconnect power from the Model 370.
This will entail removing the Ethernet
connection that is providing PoE pow-
er.
2. Remove the cover from the Model 370.
Begin by removing the four Phillips-
head screws (#1 screwdriver 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, then lift it off.
3. Locate the USB connector on the main
circuit board. It’s adjacent to the call
button. Insert the prepared USB flash
drive into it.
4. Apply power to the Model 370 by con-
necting to a Power-over-Ethernet (PoE)
Ethernet signal.
5. After a few seconds the Model 370 will
run a “boot loader” program that will
automatically load the new applica-
tion firmware file (m370.bin). This load
process takes only a few seconds.
During this time period the call button’s
LED will flash slowly in alternate col-
ors. Once the entire loading process is
over, taking approximately 10 seconds,
the Model 370 will restart using the
newly loaded application firmware.

Issue 3, May 2017 Model 370 User Guide
Page 18 Studio Technologies, Inc.
6. At this time the Model 370 is function-
ing with the newly loaded 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. Press and hold the call button, apply
power to the Model 370, and “read”
the application firmware version num-
ber by observing the two talk button
LEDs. Ensure that this is the desired
version.
Note that upon power being applied to the
Model 370 if the USB flash drive doesn’t
have the correct file (m370.bin) in the root
folder no harm will occur. Upon power up
the call button’s LEDs will flash on and off
rapidly for a few seconds to indicate this
condition and then normal operation using
the unit’s existing application firmware will
begin.
Ultimo Firmware Update
As previously discussed in this guide, the
Model 370 implements Dante connectivity
using the Ultimo 2x2 channels integrated
circuit from Audinate. The Dante Controller
software application can be used to de-
termine the version of the firmware (em-
bedded software) residing in the Ultimo
“chip.” This firmware can be updated by
way of the Model 370’s Ethernet connec-
tion. The latest Dante firmware file is avail-
able on the Studio Technologies website.
The Dante Firmware Update Manager
(FUM) application is used to install the
firmware. This program is also available
for download on the Studio Technologies
website.

Model 370 User Guide Issue 3, May 2017
Studio Technologies, Inc. Page 19
Specifications
Audio Channels: 2 talk, 2 listen
Power Source:
Power-over-Ethernet (PoE): class 1 (very low
power, ≤3.84 watts)
Network Audio Technology:
Type: Dante Audio-over-Ethernet
Bit Depth: up to 24
Sample Rate: 48 kHz
Number of Transmitter (Output) Channels: 2
Number of Receiver (Input) Channels: 2
Dante Audio Flows: 4; 2 transmitter, 2 receiver
Network Interface:
Type: twisted-pair Ethernet, Power-over-Ethernet
(PoE) supported
Data Rate: 100 Mb/s (10 Mb/s Ethernet not
supported)
Microphone Input:
Type: unbalanced, for use with dynamic
microphones
Gain: 40 or 46 dB, selectable, ref. –60 dBu input
to Dante output (–20 dBFS nominal)
Frequency Response: 50 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.02%
Dynamic Range: 75 dB
Compressor:
Threshold: 1 dB above nominal level (–19 dBFS)
Slope: 2:1
Status LED: compressor active
Headphone Output:
Type: dual-channel
Compatibility: intended for connection to mono
or stereo headsets or earpieces with nominal
impedance of 50 ohms or greater
Maximum Output Voltage: 3.8 Vrms, 1 kHz,
150 ohm load
Frequency Response: 20 Hz to 10 kHz, –3 dB
Distortion (THD+N): <0.002%
Dynamic Range: >100 dB
Call Signal Support:
Method: 20 kHz, ±800 Hz, within audio channels
Call Send Level: –20 dBFS
Call Receive Level: –27 dBFS minimum
Connectors:
Headset: 5-pin female XLR
Ethernet: Neutrik etherCON RJ45
USB: type A receptacle (located inside Model
370’s enclosure and used only for firmware
updates)
Dimensions (Overall):
3.6 inches wide (9.2 cm)
1.6 inches high (4.0 cm)
4.8 inches deep (12.6 cm)
Mounting: intended for portable applications; con-
tains integral belt clip; optional mounting adapter
kit allows Model 370 to be permanently mounted
Weight: 0.6 pounds (0.3 kg)
Specifications and information contained in this
User Guide subject to change without notice.