Model 371A Intercom Beltpack
User Guide
Issue 1, June 2018
This User Guide is applicable for serial numbers
M371A-02501 and later with application firmware 1.1 and later
and Dante® firmware 1.0.0 (UltimoX2 4.1.2.1) and later
Copyright © 2018 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50655-0618, Issue 1
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MODEL 371A
INTERCOM BELTPACK
Table of Contents
Revision History ............................................................ 4
Introduction ................................................................... 5
Getting Started .............................................................. 7
Operation ...................................................................... 12
Technical Notes ............................................................. 16
Specifications ................................................................ 21
Model 371A User Guide Issue 1, June 2018
Studio Technologies, Inc. Page 3
Revision History
Issue 1, June 2018:
1. Initial release.
MODEL 371A
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Introduction
The Model 371A Intercom Beltpack
begins with the features offered by
2-channel broadcast-style party-line
intercom user devices then adds support
for traditional single-channel headsets.
Applications that have traditionally deployed single-channel analog party-line
intercom systems from firms such as
Clear-Com® can now easily upgrade to a
high-performance dual-channel system. To
maintain compatibility and user familiarity,
legacy headsets that use a 4-pin female
XLR connector are directly compatible.
The Model 371A includes a range of new
capabilities, along with the advanced performance and flexibility that Dante® audioover-Ethernet provides. Over a standard
IP network, multiple Model 371A 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 using the STcontroller software application.
Configurable parameters include electret
microphone powering, microphone preamplifier gain, sidetone level, and talk
button operation. User features include
microphone dynamic range control, 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
371A 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 connection provides both power and
bidirectional digital audio. A broadcast
or intercom-style headset with a dynamic
or electret (low-voltage DC-powered)
microphone interfaces with unit using a
4-pin XLR connector. The Model 371A’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 371A’s
audio channels is excellent, with low
distortion, low noise, and high headroom. Careful circuit design and rugged
components ensure long, reliable operation. A wide range of applications can
be supported, including theater facilities,
over-the-air and streaming broadcasting,
Figure 1. Model 371A Intercom Beltpack top and bottom views
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corporate and government AV installations,
aerospace command and control, and
post-production facilities.
Dante Audio-over-Ethernet
Audio data is sent to and received from
the Model 371A using the Dante audioover-Ethernet media networking technology. As a Dante-compliant device, the
Model 371A’s two audio output (Dante
transmitter) and two audio input (Dante
receiver) channels can be interconnected
(routed) with other devices using the Dante
Controller software application. The Dante
transmitter 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 371A is AES67 compatible and compliant with the Dante Domain
Manager™ software application.
Two bi-color LEDs provide an indication
of the Dante connection status. The Dante
Controller’s Identify command takes on a
unique role with the Model 371A. 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 371A’s completely “pro”
performance is counter to the less-thanstellar reputation of typical party-line (PL)
intercom audio. A low-noise, wide dynamic-range microphone preamplifier and associated voltage-controlled-amplifier (VCA)
dynamics controller (compressor) ensures
that microphone audio quality is preserved
while minimizing the chance of signal
overload. DC power to support electret
microphones can be enabled if necessary.
The output of the microphone preamp and
compressor is routed to an analog-to-digital converter (ADC) section that supports
a sampling rate of 48 kHz with a bit depth
of up to 24. The audio signal, now in the
digital domain, travels through the processor and on to the Dante interface section
where it is packetized and prepared for
transport over Ethernet.
Audio input signals arrive via two Dante receiver channels. The supported sampling
rate is 48 kHz with a bit depth of up to 24.
The audio signals pass into the Model
371A’s processor where channel routing,
headphone level control, and sidetone
creation are performed within the digital
domain. Two push-in/push-out (“pop out”)
rotary controls make it easy to set and
maintain the desired headphone output
level. The audio signal destined for the
headphone output is sent to a high-performance digital-to-analog converter and
then on to a robust driver circuit. A high
signal level can be provided to a variety of
headsets, headphones, and earpieces.
Call Function
A call function allows Model 371A users to
send and receive channel-specific visual
alert signals. Pressing the call pushbutton on the top of the unit is all that’s required to signal other users that attention
is requested. Using 20 kHz tones, the call
signals are sent within the audio channels (“in band”) allowing interoperability
between multiple Model 371A units as well
as being compatible with legacy party-line
intercom systems. The call function 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 realtime cues to production personnel during
the running of live events.
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Configuration Flexibility
A highlight of the Model 371A 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 communicates with the Model 371A by way
of an Ethernet network connection. Configurable parameters include microphone
power and preamplifier gain, sidetone audio operation, and talk button operation.
The microphone input can be selected for
compatibility with dynamic or elected (DCpowered) microphones. The gain of the
microphone preamplifier can be selected
from among four choices, two for supporting dynamic microphones and two for
supporting electret microphones. These
choices allow compatibility with the variety
of microphones that are part of broadcast
and intercom headsets.
A unique Model 371A 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.
The Model 371A’s operating power is
provided by way of the Ethernet interface
using the 802.3af Power-over-Ethernet
(PoE) standard. This allows fast and efficient interconnection with the associated
data network. To support PoE power management, the Model 371A’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 371A 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 371A 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.
Getting Started
What’s Included
Ethernet Data and PoE
The Model 371A connects to an Ethernet
data network using a standard 100 Mb/s
twisted-pair Ethernet interface. The physical 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 highreliability environments. An LED displays
the status of the network connection.
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Included in the shipping carton are a
Model 371A 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
applications an Ethernet switch with the
required PoE capability will be utilized.
Connections
In this section signal interconnections
will be made using the two connectors
MODEL 371A
INTERCOM BELTPACK
located on the bottom of the Model 371A’s
enclosure. An Ethernet data connection
with Power-over-Ethernet (PoE) capability
will be made using either a standard RJ45
patch cable or an etherCON protected
RJ45 plug. A headset that has a cablemounted 4-pin female XLR connector will
be plugged into the Model 371A’s 4-pin
male headset connector.
Ethernet Connection with PoE
A 100BASE-TX Ethernet connection that
supports Power-over-Ethernet (PoE) is required for Model 371A operation. This one
connection will provide both the Ethernet
data interface and power for the Model
371A’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 371A supports Ethernet switch power management, enumerating itself as a PoE class 1 device. Any
source that is compliant with the IEEE®
802.3af standard will function correctly.
Should the selected Ethernet switch port
support Energy-Efficient Ethernet (EEE) it
must be disabled to help ensure reliable
Dante operation.
of an intercom or broadcast-style headset.
Refer to Figure 2 for connection details.
The microphone input connections are
compatible with most unbalanced dynamic
or electret (low-voltage DC-powered)
microphones. A balanced dynamic microphone should, in most cases, also function
correctly if its signal – (low) is connected to
Model 371A’s mic in –/shield connection.
No support is provided for microphones
that require P12 or P48 phantom power.
In most cases headsets associated with
single-channel party-line intercom systems will be directly compatible. A monaural (single-ear or “single-muff”) headset
should be wired such that its –/shield/
screen lead is connected to pin 3 and its
+ lead is connected to pin 4. To allow users of stereo (dual-ear or “double-muff”)
headsets to hear the Model 371A’s headphone output in both ears requires that
both its –/shield/screen leads be connected to pin 3 and both its + leads be connected to pin 4.
The Ethernet connection is made by way
of a Neutrik etherCON protected RJ45
receptacle that is located on the bottom of
the Model 371A’s enclosure. This allows
connection by way of a cable-mounted
etherCON connector or a standard RJ45
plug. The Model 371A’s Ethernet interface
Figure 2. Headset connection pinout chart
Dante Configuration
supports auto MDI/MDI-X so that a crossover cable will never be required.
For audio to pass to and from the Model A
requires that several Dante-related pa-
Headset Connection
The Model 371A provides a 4-pin male
XLR connector that interfaces with the
microphone and headphone connections
rameters be configured. These configuration settings will be stored in non-volatile
memory within the Model 371A’s circuitry.
Configuration will typically be done with
the Dante Controller software applica-
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MODEL 371A
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tion 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 371A uses the Ultimo 2-input/
2-output integrated circuit to implement the
Dante architecture.
The two Dante transmitter (Tx) channels
associated with the Model 371A’s Dante
interface must be assigned to the desired
receiver (Rx) channels. This achieves routing the Model 371A’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 combination of
the two. If the Model 371A’s transmitter
channels need to be routed using 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 371A’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 371A’s
headphone output.
The Model 371A supports an audio sample
rate of 48 kHz with no pull-up/pull-down values available. The Model 371A can serve as
the clock master for a Dante network but in
most cases it will be configured to “sync” to
another device that is serving as the “grand
master” for the Dante implementation.
The Model 371A has a default Dante
device name of ST-M371A- followed by a
unique suffix. The suffix identifies the specific Model 371A that is being configured.
The suffix’s actual alpha 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 the Dante
Controller application the default device
name and channel names can be revised
as appropriate for the specific application.
Model 371A Configuration
Many of the Model 371A’s operating
parameters 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 versions
1.06.00 and later is required to support the
Model 371A. If necessary, 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 371A unit
or units that are to be configured.
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STcontroller allows observation and selection of functions that include:
• Microphone input type (dynamic or
electret)
• Microphone preamplifier gain
• Sidetone level
• Mic kill support
• Talk button operation
Changes made using STcontroller will be
immediately reflected in the unit’s operation; no Model 371A “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 distinctive 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 371A units that are recognized will
appear in the device list. Use the Identify
command to allow easy recognition of a
specific Model 371A 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 Type
Choices are Dynamic and Electret.
If the associated headset has a dynamic
(non-powered) microphone select the
Dynamic input type. If the headset has
an electret microphone that requires a
source of low-voltage DC power for operation select Electret. Note that the Model
371A cannot supply P12 or P48 phantom
power that may be required for balanced
condenser (capacitor) microphones. This
should not pose an issue as this type of
microphone is essentially never associated with a headset that would be used for
intercom applications.
Microphone Preamplifier Gain
Choices are Low (42 dB) and High (48 dB)
for dynamic input type and Low (22 dB)
and High (30 dB) for electret input type.
A total of four microphone preamplifier
gain settings are provided. Which are
available depends on the configuration
of the microphone input type. Dynamic
microphones have an output level that is
typically lower than that provided by electret microphones. As such, the gain associated with the low and high settings when
the input type is Dynamic are significantly
greater than the gain choices available
when the input type is Electret.
When the input type is Dynamic the Low
(42 dB) gain setting 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.) The Low (42 dB) gain setting
could also be valuable should the connected microphone have a high sensitivity
(high output level for a given acoustical
input) or an enthusiastic user routinely
talks loudly into the microphone. Setting
the gain for High (48 dB) may be helpful in
some applications, such as with headsets
that have a low microphone output level.
The higher gain setting may also be useful
when the Model 371A 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.
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Electret microphones typically have a
higher output level due to their internal
preamplifier. As such less preamplifier gain
is required. Select either the Low (22 dB)
or High (30 dB) setting as appropriate for
the application.
The compressor active LED, visible on
the bottom of the Model 371A’s enclosure
adjacent to the headset connector, can
act as a guide when setting the microphone preamp gain. During normal talk
operation the compressor active LED
should light intermittently. If, for example,
with a dynamic microphone the LED
rarely lights and the preamp gain is set
to Low (42 dB) it might be a good idea to
change it to High (48 dB). If the LED is lit
fully during normal talking in a situation
where the headset has an electret microphone and the gain is set for High (30 dB),
changing it to Low (22 dB) might be a
good idea.
Sidetone Level
Choices are Off, Low, Medium Low,
Medium, Medium High, and High.
The Model 371A includes a sidetone function that allows microphone audio coming
from the microphone preamplifier to be
sent to the headphone output. This serves
as a user confirmation that they are actively sending audio to one or more of the
talk output channels. Sidetone audio will
only be routed to the headphone output
when either or both of the talk channels is
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. Sidetone audio can also be disabled by selecting 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.
Mic Kill Support
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 control. 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 disable all
active talk channels. The Device ID method
uses the identification command generated
by the Dante Controller or STcontroller software applications as a “trigger” to disable
any active talk channels. The I can be generated by applications that incorporate the
Studio Technologies’ proprietary method.
This method utilizes sending a data command over the Ethernet connection. Select
the desired mic kill configuration from the
four choices. Off simply means that no remote talk control is supported.
Talk Button Operation
Choices are Push to Talk, Latching, Push
to Talk/Tap to Latch, and Disabled.
This configuration section allows independent selection of how the two talk buttons
will function. When the Push to Talk mode
is selected the operation is self-explanatory.
Only when a talk button is pressed and held
will talk audio be sent out its associated
Dante transmitter channel.
When the Latching mode is selected tapping (momentarily pressing) the button will
cause the function to “latch” into the talk
active mode. Tapping the button again will
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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 transmitter channel. Tapping (momentarily
pressing) the button will cause the function to “latch” into the talk active mode.
Tapping the button again will cause the
function to “unlatch” and talk will no
longer be active.
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 situations when the Latching or Push to Talk/
Tap to Latch modes setting will prove to
be very useful.
When the Disabled mode is selected
microphone audio will never be sent out
the associated Dante transmitter 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.
Using the Studio Technologies STcontroller
software application the unit’s configuration should have been selected to meet
the needs of the specific application. The
Model 371A’s Dante configuration settings
should have been selected using the Dante
Controller software application. In this way
the Model 371A’s two audio output channels (Dante transmitter channels) and two
audio input channels (Dante receiver channels) should have been routed, by way of
Dante “subscriptions,” to the receiver and
transmitter channels on associated Danteenabled equipment.
Initial Operation
The Model 371A 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 commence. 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
connections are established. The green
and orange LEDs that illuminate the three
pushbutton switches on the top panel may
initially light randomly and then will light in
a test sequence to indicate that the application firmware (embedded software)
has started. Once the entire sequence has
completed and the Dante connection has
been established full operation will begin.
Operation
At this point everything should be ready
and Model 371A operation can commence. An Ethernet connection with
Power-over-Ethernet (PoE) capability
should have been made. A headset terminated with a cable-mounted 4-pin female
XLR connector should be plugged into the
headset connector.
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Ethernet and Dante Status
LEDs
Three status LEDs are located below the
etherCON RJ45 receptacle on the Model
371A’s bottom panel. The LINK ACT LED
will light green whenever an active connection to a 100 Mb/s Ethernet network has
been established. It will flash in response
to Ethernet data packet activity. The SYS
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INTERCOM BELTPACK
and SYNC LEDs display the operating status of the Dante interface and associated
network. The SYS LED will light red upon
Model 371A 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 371A is not synchronized with
a Dante network. It will light solid green
when the Model 371A 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 371A 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.
Compressor Active LED
A yellow LED indicator is located on the
bottom panel adjacent to the headset
connector. Labeled COMP, the LED displays the status of the microphone audio
compressor function. It will light whenever
the input level from the microphone, along
with the configured preamplifier gain, is
such that the dynamic range of the talk
signal is being controlled. It’s perfectly acceptable for this LED to light intermittently
whenever a user is talking at a normal
voice level into the associated microphone. But if the COMP LED lights solid
while a user is talking at a normal voice
level this will 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 beneficial. Note that due to the design of the
circuitry the compressor active LED will
function whether or not either or both of
the talk channels are active.
Headphone Output
Two rotary potentiometers (“pots”), located on the Model 371A’s top panel,
allow individual adjustment of the level of
the two audio input signals as they are
sent to the headphone output. The audio
signal that is sent to the headphone output will be the sum (mix) of the two input
signals. The pots are “push in/push out”
type which allow their associated knobs
to be in their “out” position to be adjusted
and then moved to their “in” position when
protection from an unwanted change is
desired
Users should 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 371A’s processor which then adjusts the signal level
within the digital domain. When a pot is
in its fully counterclockwise position the
associated audio signal is fully muted.
The on/off status of the 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 371A’s two talk channels.
How they function will depend on the configuration 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
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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
active the green LED will light. The button will not be lit when the function is not
active.
Push to Talk/Tap to Latch
If a button has been 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. Momentarily pressing
(“tapping”) the button will cause the function to change states; off-to-on or on-tooff. Whenever the talk function is active the
green LED will light. The button will not be
lit when the function is not active.
Disabled
and will provide Model 371A users with
a confidence signal that they are actively
talking to other intercom users. The exact
sidetone level is configured from among
five values within the STcontroller application. There is also a selection choice for
turning off sidetone. There is no means
of adjusting the sidetone level using a
physical button or control on the Model
371A 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.
A button that is configured to the Disabled
mode will never allow talk audio to be
sent to the associated Dante audio output
channel. But to provide “feedback” that
the button 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!”
Call Function
An integrated call function allows Model
371A users, and users of compatible
equipment, to signal to each other visually. Individual call functions are provided
for each of the two talk channels. Either
or both can have its call function active at
any one time. Technically call is achieved
by sending a 20 kHz audio tone on the
Sidetone Function
The Model 371A includes a sidetone function that sends microphone audio to the
headphone output whenever one or both
of the talk buttons are active. The quality
of the sidetone audio should be excellent
Issue 1, June 2018 Model 371A User Guide
Page 14 Studio Technologies, Inc.
desired audio output channel. This signal
is summed (mixed) with normal talk audio.
The Model 371A’s two audio input channels continually monitor for the presence
of 20 kHz. A call signal recognized when a
continuous 20 kHz tone is detected on the
audio input for that channel.
MODEL 371A
INTERCOM BELTPACK
Normal talk audio signals will not be confused with a call signal. Digital filters within
the Model 371A’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 receiver) signals before they are sent to the
headphone output. This prevents users
with extended high-frequency sensitivity,
such as hosts and guests associated with
dog shows, from receiving undesirable
audio content.
To send a call signal is simple: just enable either or both of the talk buttons and
simultaneously press and hold the call
button. When call sending is active the orange LED associated with the call button
will light. At the same time the channel or
channels that are active in their talk mode
will have their associated orange LED
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 371A audio input channel 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 signal on either or both audio input channels
the orange LED associated with the call
button will not light.
By using a 20 kHz tone for call signaling
the Model 371A is compatible with legacy
intercom equipment, including the venerable RTS BP-325. When interconnecting
Model 371A 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 ClearCom method of call functionality is also
possible by using the Model 45DC Intercom Interface. (It converts the DC call signal associated with pin 3 of a Clear-Com
party-line circuit to a 20 kHz tone.) Also,
devices such as the Studio Technologies
Model 44D Audio Interface will send and
receive 20 kHz signals that are be compatible with the Model 371A. 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 presence of 20 kHz call signals. If call signals
are detected the GPO (general-purpose
output) signals will activate.
How to Identify a Specific
Model 371A
The Dante Controller software application offers an Identify command that can
be used to help locate a specific Model
371A. When Identify is selected it will send
a command to a single Model 371A 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 bottom panel, will slowly flash green. After a
few seconds the LED identification pattern
will cease and normal Model 371A button
LED and Dante status LED operation will
resume.
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If configured, the Identify command can
also cause the mic kill function to activate.
For details please refer to the next paragraph of this guide.
Mic Kill Function
The Model 371A includes a mic kill function, allowing talk buttons that have been
placed in their enabled (on) state to be
remotely changed to their disabled (off)
state. This allows one or both talk channels on a specific Model 371A that have
been enabled to be remotely disabled.
The reason for this function is simple. It’s
common in intercom applications for users to enable a talk channel and then go
“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 371A is identified using the Identify command within Dante Controller or
STcontroller any enabled talk channel
will be forced to its disabled state. If the
Global Kill Command method is enabled
the Model 371A will respond to any such
request and force all talk channels to their
disabled state.
Technical Notes
IP Address Assignment
By default the Model 371A’s Ethernet interface will attempt to automatically obtain
an IP address and associated settings
using the DHCP (Dynamic Host Configuration Protocol). If a DHCP server is not
detected an IP address will automatically
be 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 interconnected using an RJ45 patch cable will, in
most cases, correctly acquire IP addresses and be able to communicate with each
other.
An exception does arise when trying to
directly interconnect two Dante-enabled
devices that use Ultimo integrated circuits
to implement Dante. The Model 371A uses
the Ultimo “chip” and, as such, a direct
one-to-one interconnection to another
Model 371A (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 371A operation it’s highly unlikely that an application
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would use two Model 371A units without
a PoE-enabled Ethernet switch being
present.
Using the Dante Controller software
application the Model 371A’s IP address
and related network parameters can be
manually set for a fixed (static) configuration. 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 capability 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
static IP address. If knowledge of a Model
371A’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 Windows OS the arp –a command can be
used to display a list of LAN information
that includes MAC addresses and corresponding IP addresses. The simplest
means of identifying an unknown IP address is to create a “mini” LAN with a
small PoE-enabled Ethernet switch connecting a personal computer to the Model
371A. Then by using the appropriate ARP
command the required “clues” can be
obtained.
Optimizing Network
Performance
For best Dante audio-over-Ethernet performance a network that supports VoIP
Quality-of-service (QoS) capability is rec-
ommended. This can 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 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 connected 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 371A’s application
firmware (embedded software) can be
identified. One requires only the Model
371A unit and involves a button-press
sequence performed upon power up. The
other method utilizes the Model 371A and
the STcontroller software application. Either method may prove to be useful when
working with factory personnel on application support and troubleshooting.
As part of the Model 371A’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
Ethernet cable. Upon application of PoE
power the Model 371A 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
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MODEL 371A
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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 371A.
A selection in the STcontroller software
application allows the Model 371A’s application firmware version to be identified. Connect the Model 371A unit to the
network and let it connect and start to
function. Then, after starting STcontroller,
review the list of identified devices and
select the specific Model 371A that interests you. Then select Version under the
Device tab. A page will then display that
will provide lots of useful information. This
includes the application firmware version
and well as details on the firmware present
in the Ultimo integrated circuit.
Application Firmware Update
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
M371A.bin. Studio Technologies will supply the application 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
371A, the name of the zip file itself will
include the file’s version number. For example, a file named M371Av1r2MCU.zip
would indicate that version 1.2 of the application firmware (M371A.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 be loaded into the processor’s flash memory. The
precise steps required will be highlighted
in the next paragraphs of this guide.
Procedure
It’s possible that updated versions of the
application firmware (embedded software)
that is utilized by the Model 371A’s processor (microcontroller or MCU) integrated circuit will be released to add features
To update the application firmware file
follow these steps:
1. Disconnect power from the Model
371A. This will entail removing the
Ethernet connection that is providing
PoE power.
or to correct 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 nonvolatile flash memory by way of a USB
interface. The Model 371A implements a
USB host function that directly supports
connection of a USB flash drive. The
Model 371A’s MCU updates its application
firmware using a file named M371A.bin.
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2. Remove the cover from the Model
371A. Begin by removing the four
Phillips-head machine screws (#1
screw driver tip), two per side. Be
certain to save the screws so that reassembly 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.
MODEL 371A
INTERCOM BELTPACK
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 371A by
connecting to a Power-over-Ethernet
(PoE) Ethernet source.
5. After a few seconds the Model 371A
will run a “boot loader” program that
will automatically load and save the new
application firmware file (M371A.bin).
This will take only a few seconds. During
this time period the call button’s LED will
flash slowly in alternate colors. Once the
entire process is over, taking approximately 10 seconds, the Model 371A will
restart using the newly-saved application
firmware.
6. At this time the Model 371A is operating
under the newly-saved application firmware and the USB flash drive can be
removed. But to be conservative, remove PoE power first and then
remove 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 371A, 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 version number. Whatever method
you use, ensure that the desired version
is present.
8. Once the update process has been
completed reverse the steps and reattached the cover using the four machine
screws.
Note that upon power being applied to the
Model 371A if a connected USB flash drive
doesn’t have the correct file (M371A.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 firmware will begin.
Ultimo Firmware Update
As previously discussed in this guide,
the Model 371A implements Dante connectivity using the 2-input/2-output Ultimo
integrated circuit from Audinate. The Dante
Controller software application can be used
to determine the version of the firmware
(embedded software) that resides in the
Ultimo “chip.” The STcontroller software
application can also be used to identify
the Ultimo’s firmware version. (Use the
Version selection under the Device tab.)
The Ultimo firmware can be updated by
way of the Model 371A’s Ethernet connection. The latest Ultimo firmware file
is available on the Studio Technologies
website. The Dante Firmware Update Manager (FUM) application program is used to
install the Ultimo firmware. This program is
also available for download on the Studio
Technologies website. It’s anticipated that
an updated version of the Dante Controller
software application will include an automated method of updating Ultimo firmware.
It should offer a much simpler method of
keeping the Ultimo firmware current.
Model 371A versus Model 371
Some users may be interested in the
differences between the original Model 371
Intercom Beltpack and the newer Model
371A that is described in this guide. A
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MODEL 371A
INTERCOM BELTPACK
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 371A are performed using the STcontroller software application. STcontroller also allows the version numbers
of the Model 371A’s application firmware (embedded software) and Ultimo
firmware to be remotely identified.
• Support for electret microphones was
added to the Model 371A. This involved
adding a 5 volt DC power source to the
microphone input circuitry. This power
source can be enabled or disabled as
required using STcontroller.
• The configurable microphone input gain
settings were modified to be compatible
with the increased output level supplied
by electret microphones.
• The DIP switch assembly on the Model
371 is not present on the Model 371A.
As such the belt clip no longer needs
to be rotated and its mounting arrangement has been changed.
• The user-accessible sidetone trim potentiometer found on the Model 371
is not present on the Model 371A. In
the Model 371A the level of the sidetone function is configured using
STcontroller.
• The Model 371A offers a second method of activating the mic kill function. This
allows a data signal, in additional to the
Device ID command, to activate mic kill.
Belt Clip
The belt clip is attached to the back of the
Model 371A’s enclosure by way of two 6-32
thread, Philips-head machine screws. Unlike other the original Model 371 Intercom
Beltpack units, the belt clip on the Model
371A will never have to be rotated as part
of the configuration process. (There are no
configuration DIP switches under the belt
clip.) But if the belt clip does need to be
replaced a #1 Philips-head screw driver
would be the correct tool to remove the
machine screws.
Restoring Factory Defaults
A command in the STcontroller software
application allows the Model 371A’s configuration to be reset to the factory default
values. From STcontroller select the Model
371A for which you want to restore its
defaults. Select the Device tab and then
select the Factory Defaults feature. Then
click on the OK box. The values shown on
the screen should reflect the default values.
They are:
Microphone Input Type: Dynamic
Microphone Preamplifier Gain:
Low (42 dB)
Sidetone Level: Medium
System Mic Kill: Device ID/Global Kill
Command
Button Operation – Channels 1 and 2:
Push to Talk/Tap to Latch
• The STcontroller software application
now offers the ability to configure the
mic kill function, including allowing it to
be disabled.
Issue 1, June 2018 Model 371A User Guide
Page 20 Studio Technologies, Inc.
MODEL 371A
INTERCOM BELTPACK
Specifications
Power Source:
Power-over-Ethernet (PoE):
power, ≤3.84 watts) per IEEE® 802.3af
Network Audio Technology:
Type: Dante audio-over-Ethernet
AES67-2013 Support: yes
Dante Domain Manager (DDM) Support: yes
Bit Depth: up to 24
Sample Rate: 48 kHz
Number of Transmitter (Output) Channels:
Number of Receiver (Input) Channels: 2
Dante Audio Flows: 4; 2 transmitter, 2 receiver
Network Interface:
Type: 100BASE-TX, twisted-pair Ethernet,
Power-over-Ethernet (PoE) supported
Data Rate: 100 Mb/s (10 Mb/s and 1000 Mb/s
“GigE” Ethernet not supported)
Audio Channels: 2 talk, 2 listen
Microphone Input:
Compatibility: dynamic or electret (low-voltage
DC-powered) microphones
Type: unbalanced
Electret Microphone Power:
resistor, selectable on/off
Gain, configured for dynamic microphones:
42 or 48 dB, selectable, ref. –60 dBu input to Dante
output (–20 dBFS nominal)
Gain, configured for electret microphones:
22 or 30 dB, selectable, ref. –60 dBu input to Dante
output (–20 dBFS nominal)
Frequency Response:
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
class 1 (very low
2
5 volts DC via 2.21 k
50 Hz to 10 kHz, –3 dB
Headphone Output:
single-channel (sum (combination) of audio
Type:
input 1 and audio input 2)
Compatibility: intended for connection headsets
with nominal impedance of 50 ohms or greater
Maximum Output Voltage:
150 ohm load
Frequency Response:
Distortion (THD+N): <0.002%
Dynamic Range: >100 dB
Call Function:
Signaling Method: 20 kHz, ±800 Hz, within audio
channels
Call Send Level: –20 dBFS
Call Receive Level: –27 dBFS minimum
Connectors:
Headset: 4-pin male XLR (Associated headset re-
quires 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 NE8FBH etherCON RJ45
receptacle
USB: type A receptacle (located inside l 371A’s
enclosure and used only for application firmware
updates)
Configuration: requires Studio Technologies
STcontroller software application, version 1.06.00
and later (STcontroller is compatible with Windows
version 7 and later)
Environmental:
Operating Temperature:
(32 to 122 degrees F)
Storage Temperature:
(–40 to 158 degrees F)
Humidity: 0 to 95%, non-condensing
Altitude: not characterized
Dimensions (Overall):
3.6 inches wide (9.2 cm)
1.6 inches high (4.0 cm)
4.8 inches deep (12.6 cm)
Mounting: intended for portable applications; contains integral belt clip; optional MBK-01 Mounting
Bracket Kit allows Model 371A to be permanently
mounted
Weight:
0.6 pounds (0.3 kg)
3.8 Vrms, 1 kHz,
20 Hz to 10 kHz, –3 dB
0 to 50 degrees C
–40 to 70 degrees C
Specifications and information contained in this
User Guide subject to change without notice.
Model 371A User Guide Issue 1, June 2018
Studio Technologies, Inc. Page 21
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