Studio Technologies 371A Users Manual
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
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Revision History
Issue 1, June 2018:
1. Initial release.
MODEL 371A
INTERCOM BELTPACK
Issue 1, June 2018 Model 371A User Guide
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MODEL 371A
INTERCOM BELTPACK
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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MODEL 371A
INTERCOM BELTPACK
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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MODEL 371A
INTERCOM BELTPACK
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
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