Studio Technologies 371 User manual

Copyright © 2017 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50633-0317, Issue 2
User Guide
Issue 2, March 2017
This User Guide is applicable for serial numbers
M371-00151 and later with application firmware 1.2 and later
and Dante firmware 1.2.0 (UltimoX2 3.10.3.1) and later
Model 371 Intercom Beltpack

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Model 371 User Guide Issue 2, March 2017
Studio Technologies, Inc. Page 3
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 7
Operation ...................................................................... 11
Technical Notes ............................................................. 14
Specifications ................................................................ 18

Issue 2, March 2017 Model 371 User Guide
Page 4 Studio Technologies, Inc.
Revision History
Issue 2, March 2017:
1. Cover page revised to reflect correct application and Dante firmware release numbers.
Issue 1, January 2017:
1. Initial release.

Model 371 User Guide Issue 2, March 2017
Studio Technologies, Inc. Page 5
Introduction
The Model 371 Intercom Beltpack com-
bines the features offered by broadcast-
style 2-channel party-line (PL) intercom
user devices with a single-channel listen
output and a 4-pin male XLR headset
interface connector. This output arrange-
ment allows deployment in PL intercom
applications where support for single-ear
headsets is desired. These headsets,
which utilize dynamic microphones, are
widely used in theatrical, corporate, and
industrial applications where it’s important
to have one ear remain open to ambient
audio signals.
The Model 371 uses the advanced ca-
pabilities that Dante audio-over-Ethernet
can provide. Over a standard IP network,
multiple Model 371 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 compati-
ble matrix intercom systems. Only a single
Power-over-Ethernet (PoE) connection is
required for operation. Key user features
can be easily configured including micro-
phone preamplifier gain and talk button
operation. Additional 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 371 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
headset with a dynamic microphone inter-
faces to the unit using a cable-mounted
4-pin female XLR connector. The connected
headset can be either single- or dual-ear
models but the Model 371 has only a single
channel headphone audio output; the two
listen audio channels are always combined
and sent to the one audio output. Three 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 headphone output volume as well
as maintaining the desired settings. The
Model 371’s enclosure is made from an
aluminum 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 371’s two
audio channels is excellent, with low distor-
tion, low noise, and high headroom. Careful
Figure 1. Model 371 Intercom Beltpack top and bottom views

Issue 2, March 2017 Model 371 User Guide
Page 6 Studio Technologies, Inc.
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 industrial facilities.
Dante Audio-over-Ethernet
Audio data is sent to and received from
the Model 371 using the Dante audio-over-
Ethernet media networking technology. As
a Dante-compliant device, the Model 371’s
two output (Dante transmitter) and two in-
put (Dante receiver) audio channels can be
assigned to other devices (routed) using
the Dante Controller software application.
The Dante transmitter and receiver chan-
nels are limited to supporting four Dante
flows, two in each direction. The digital
audio’s bit depth is 24 with a sampling rate
of 48 kHz. 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 371.
Not only will it cause the talk button LEDs
to light in a unique highly visible sequence,
it will also turn off any active talk channels.
Audio Quality
The Model 371’s completely “pro” perfor-
mance 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
audio 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 371’s processor. The sampling
rate is 48 kHz with a bit depth of up to 24.
Headphone level control, channel mixing
(combining), and sidetone creation are
performed in the digital domain. This pro-
vides flexibility, allows precise control, and
keeps the three user level potentiometers
(channel 1, channel 2, and sidetone) from
having to directly handle analog audio
signals. The two audio channels destined
for the headphone output are sent to a
high-performance 2-channel digital-to-
analog converter and then on to a robust
driver circuit. High signal levels can be
provided to a variety of headsets, head-
phones, and earpieces.
Call Function
A call function allows Model 371 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 371 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 371 is its ability to
be easily configured to the meet the needs
of specific users and applications. Three
DIP switches allow control of the micro-
phone preamplifier gain and talk button
operation. 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 intercom and
broadcast 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.
Ethernet Data and PoE
The Model 371 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 371’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 371’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 371 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 371 uses Audinate’s Ultimo™ inte-
grated circuit. The firmware in this integrat-
ed 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 371 Intercom Beltpack and a print-
ed 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 371. An Ether-
net 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
headset will be connected using a cable-
mounted 4-pin female XLR connector.

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Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that
supports Power-over-Ethernet (PoE) is
required for Model 371 operation. This one
connection will provide both the Ethernet
data interface and power for the Model
371’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 371 supports Ether-
net switch power management, enumerat-
ing itself as a PoE class 1 device.
The Ethernet connection is made by way of
a Neutrik etherCON protected RJ45 con-
nector that is located on the bottom panel
of the Model 371. This allows connection
by way of a cable-mounted etherCON con-
nector or a standard RJ45 plug. The Model
371’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 371 was designed such that the
Ethernet connection will provide both data
and Power-over-Ethernet (PoE) power.
There may be situations where the asso-
ciated Ethernet switch does not provide
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 correctly.
Midspan units are available from a variety
of sources, including many online retailers.
Headset Connection
The Model 371 provides a 4-pin male
XLR connector that can interface with
the microphone and headphone connec-
tions of many intercom or broadcast-
style headsets. In most cases headsets
associated with single-channel party-line
intercom beltpacks will be directly com-
patible. Headset models with dynamic
microphones from vendors such as Clear-
Com®, Sennheiser, Shure®, and beyerdy-
namic should perform very well. Refer to
Figure 2 for connection details.
Figure 2. Headset connection pinout chart
The microphone input connections are
intended primarily for use with unbalanced
dynamic microphones. On the selected
headset, connect microphone common,
shield, or screen to pin 1 and microphone
+ to pin 2. Headsets with a balanced mi-
crophone should also function correctly.
Connect both microphone – and common,
shield or screen to pin 1 and microphone +
to pin 2. No support is provided for unbal-
anced or balanced microphones that re-
quire a power source including low-voltage
“eletret,” P12 phantom, or P48 phantom.
A monaural (single-ear, single-sided, or
“single-muff”) headset should be wired
such that its –, shield, or screen lead is con-
nected to pin 3 and its + lead is connected
to pin 4. To allow users of stereo (double-
ear, double- sided, or “double-muff”) head-
sets to hear the Model 371’s audio output
in both ears requires that both its -, shield,
or screen leads be connected to pin 3 and
both its + leads be connected to pin 4.

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Dante Configuration
For audio to pass to and from the Model
371 requires that several Dante-related
parameters be configured. These configu-
ration settings will be stored in non-volatile
memory within the Model 371’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 371 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 371’s Dante
interface must be assigned to the desired
receiver channels. This achieves routing the
Model 371’s two talk output audio chan-
nels 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 chan-
nels) 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 combination of the two. If the Model
371’s transmitter channels need to be rout-
ed to more than two flows it’s possible that
an intermediary device, such as a Studio
Technologies’ Model 5422 Dante Intercom
Audio Engine, can be used to “repeat” the
signals.
The two Dante receiver (Rx) channels as-
sociated with the Model 371’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 371’s head-
phone output.
The Model 371 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 371 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 371 has a default Dante device
name of ST-M371 and a unique suffix. The
suffix identifies the specific Model 371 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 ap-
propriate for the specific application.
Model 371 Configuration
Three DIP switches are used to select the
microphone preamplifier gain and how the
two talk buttons will function. These con-
figuration choices allow the performance of
the Model 371 to be optimized for specific
applications and user preferences. The
switches are accessible from the back of
the unit’s enclosure, through a small open-
ing 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 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 direction. Save the
screw so that it can be re-installed once the

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desired configuration choices have been
made. Note that the threaded fastener
within the back of the Model 371’s chas-
sis has an internal locking mechanism
(a plastic bushing) that prevents the belt
clip’s 6-32 machine screw from vibrating
loose. So no additional method of thread
locking, such as a lock washer or chemi-
cal compound, is necessary.
The three switches provide a simple set of
configuration choices. One switch allows
the gain of the microphone preamplifier to
be adjusted. The other two switches are
used to select the manner in which the
talk buttons will function. The switches are
connected to the Model 371’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 configura-
tion changes to be recognized and imple-
mented. Two additional switches are not
utilized as of the writing of this guide but
may find application at a later date.
Microphone Preamp Gain
Switch SW1 allows the gain of the micro-
phone preamplifier to be selected. When
SW1 is in the down (off) position 40 dB
of gain is selected. This will be appropri-
ate for most applications. (Technically this
gain is approximately equal to the gain
provided within an RTS® BP-325 analog
party-line beltpack.) To select 46 dB of
gain place SW1 to the up (on) position.
This additional 6 dB of gain may be helpful
in some applications, such as with head-
sets that have a low microphone output
level. The higher gain setting may also be
useful when the Model 371 is going to be
deployed at events where users are not
able to speak at normal levels, e.g., sporting
events such as golf tournaments.
The compressor active LED, visible on the
bottom of the Model 371 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 normal 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 371’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 inde-
pendently configured. The two operating
choices are push to talk and push to talk/tap
to latch. SW2 is used to select the operat-
ing mode for the talk button associated with
channel 1. SW3 is used to select the oper-
ating mode for the talk button associated
with channel 2. Many applications are best
served when the buttons are configured for
Figure 3. Microphone preamp gain
configuration switch

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Model 371’s three configuration switches
should have been used to select the de-
sired operating characteristics.
Initial Operation
The Model 371 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
371’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 371 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 371 is
not synchronized with a Dante network. It
will light solid green when the Model 371
Figure 4. Talk button mode configuration
switches
push to talk operation. This ensures that
a channel won’t accidentally be left in the
talk mode. But there will certainly be valid
situations where the push to talk/tap to
latch settings will prove to be very useful.
Operation
At this point Model 371 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 4-pin female XLR connector should
be plugged into the headset connector.
Only a headset with a dynamic micro-
phone will function correctly.
The Model 371’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

Issue 2, March 2017 Model 371 User Guide
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is synchronized with a Dante network and
an external clock source (timing reference)
is being received. It will slowly flash green
when the Model 371 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 371/Remote Talk
Off Function
The Dante Controller software applica-
tion offers an identify command that can
be used to help locate a specific Model
371. When identify is selected it will send
a command to a single Model 371 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
the bottom panel, will slowly flash green.
After a few seconds the LED identification
patterns will cease and normal Model 371
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 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 371 that
have been accidentally enabled to be re-
motely turned off. A subtle but interesting
action will also occur if the identify com-
mand is received when the Model 371 is
in a specific configuration and talk opera-
tion 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 371 that
might have had one or both of its buttons
accidentally activated.
For example, if a Model 371 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 momen-
tarily disabled, providing an aural “clue”
as to which unit is in an unwanted state
and helping guide personnel to identify
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 371’s top panel, allow adjust-
ment of the level of the two audio input
signals as they are sent to the headphone
output. The resulting audio signal that is
sent to the headphone output will be a mix
(combination) of the two input signals. The
pots are “push-in/push-out” type which
allows the associated 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 transducer(s) of the

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associated headset. Analog audio signals
do not pass directly through the rotary
level controls. The position of the pots is
recognized by the Model 371’s processor
which then adjusts 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 output. They are all indepen-
dent 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
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 371’s audio output chan-
nels. How they function will depend on the
configuration of the unit. Each button can
be configured independently. When a but-
ton has been set for push to talk mode how
it functions is pretty self-explanatory. Press
and hold the button when headset micro-
phone audio is to be sent out the associ-
ated audio output channel. The button’s
green LED will light to indicate that the out-
put is active. If the button has been config-
ured 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. Momentarily
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 371 includes a sidetone func-
tion that sends microphone audio to the
headphone output whenever either or both
of the talk functions are active. The audio
quality should be excellent and will provide
the user with a confidence signal that they
are actively talking to other intercom users.
The level of the sidetone audio is ad-
justed 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

Issue 2, March 2017 Model 371 User Guide
Page 14 Studio Technologies, Inc.
pass directly through the sidetone pot but
instead is used by the Model 371’s proces-
sor to control the level in the digital audio
domain.
Call Function
An integrated call function allows Model
371 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
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
371’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 371’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 enable
either or both of the talk buttons and simul-
taneously press and hold the call button.
When call sending is active the orange LED
associated with the call button will light. At
the same time the channel or channels that
are active in their talk mode will have their
associated orange LED 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 371 audio input channel
receives a call signal (20 kHz audio tone)
the orange LED on its companion 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 signal on either or
both channels the orange LED associated
with the call button will not light.
By using a 20 kHz tone the Model 371 is
compatible with legacy intercom equip-
ment, including the venerable RTS BP-325.
When interconnecting Model 371 and
BP-325 units using an appropriate Dante-
enabled interface, such as the Studio Tech-
nologies’ Model 45DR, call signaling is fully
compatible. Compatibility with the Clear-
Com method of call functionality is pos-
sible 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 compatible. 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.

Model 371 User Guide Issue 2, March 2017
Studio Technologies, Inc. Page 15
Technical Notes
IP Address Assignment
By default the Model 371’s Ethernet inter-
face will attempt to automatically obtain an
IP address and associated settings using
DHCP (Dynamic Host Configuration Pro-
tocol). If a DHCP server is not detected an
IP address will automatically be assigned
using the link-local protocol. This proto-
col 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 ad-
dress in the IPv4 range of 169.254.0.1 to
169.254.255.254. In this way multiple Dante-
enabled devices can be connected together
and automatically function, whether or not
a DHCP server is active on the LAN. Even
two Dante-enabled devices that are directly
interconnected using an RJ45 patch cord
will, in most cases, correctly acquire IP ad-
dresses and be able to communicate and
transport audio. An exception does arise
when trying to directly interconnect two
Dante-enabled devices that use the Ultimo
Dante implementation, such as two Model
371 units. An Ethernet switch is required
to provide the Ethernet ports to correctly
interconnect two Ultimo-based devices di-
rectly with each other. (The technical reason
relates to the need for the slight latency
provided by an Ethernet switch.)
Using the Dante Controller software ap-
plication the Model 371’s IP address and
related 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 371’s IP
address has been misplaced there is no re-
set 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 Windows
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 iden-
tifying an unknown IP address is to create a
“mini” LAN with a personal computer con-
nected directly to the Model 371. 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 371’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 troubleshooting.

Issue 2, March 2017 Model 371 User Guide
Page 16 Studio Technologies, Inc.
Before connecting the PoE Ethernet cable,
press and hold the call button. Then con-
nect the Ethernet cable. Upon application
of power the Model 371 will go through its
normal power-up sequences followed by
a display of the firmware version. The LED
associated 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 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 “flashes”
once followed by the channel 2 talk button
“flashing” twice this would indicate that
application firmware version 1.2 was pres-
ent in the Model 371.
Application Firmware Update
Procedure
It’s possible that updated versions of the
application firmware (embedded software)
that is utilized by the Model 371’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-vol-
atile memory by way of a USB interface.
The Model 371 implements a USB host
function that directly supports connec-
tion of a USB flash drive. The Model 371’s
MCU updates its firmware using a file
named m371.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 m371.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 371, the name of
the zip file itself will include the file’s ver-
sion number. For example, a file named
m371v1r1MCU.zip would indicate that
version 1.1 of the application firmware
(m371.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
follow these steps:
1. Disconnect power from the Model 371.
This will entail removing the Ethernet
connection that is providing PoE
power.
2. Remove the cover from the Model 371.
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.

Model 371 User Guide Issue 2, March 2017
Studio Technologies, Inc. Page 17
4. Apply power to the Model 371 by con-
necting to a Power-over-Ethernet (PoE)
Ethernet signal.
5. After a few seconds the Model 371 will
run a “boot loader” program that will
automatically load the new applica-
tion firmware file (m371.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 371 will restart using the
newly loaded application firmware.
6. At this time the Model 371 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 371, 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 371 if the USB flash drive doesn’t
have the correct file (m371.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 371 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 371’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.

Issue 2, March 2017 Model 371 User Guide
Page 18 Studio Technologies, Inc.
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: single-channel (combination of audio input 1
and audio input 2)
Compatibility: intended for connection to
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: 4-pin male XLR (intended for interfacing
with a cable-mounted 4-pin female XLR connector
wired with pin 1 mic –/shield/screen; pin 2 mic +;
pin 3 headphone –; and pin 4 headphone +)
Ethernet: Neutrik etherCON RJ45
USB: type A receptacle (located inside Model
371’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;
contains integral belt clip; optional mounting
adapter kit allows Model 371 to be permanently
mounted
Weight: 0.6 pounds (0.3 kg)
Specifications and information contained in this
User Guide subject to change without notice.