Studio Technologies 372A Users Manual
Model 372A Intercom Beltpack
User Guide
Issue 1, April 2019
This User Guide is applicable for serial numbers
M372A-00151 and later with application firmware 1.1 and later
Copyright © 2019 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50691-0419, Issue 1
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MODEL 372A
INTERCOM BELTPACK
Table of Contents
Revision History ........................................................... 4
Introduction ................................................................... 5
Getting Started ............................................................. 8
Operation ...................................................................... 13
Technical Notes ............................................................ 17
Specifications ............................................................... 21
Appendix A ................................................................... 22
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Revision History
Issue 1, April 2019:
• Initial release.
MODEL 372A
INTERCOM BELTPACK
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MODEL 372A
INTERCOM BELTPACK
Introduction
The Model 372A Intercom Beltpack is
a highly compact user-worn device that
combines a single channel of talk and two
channels of listen. The unit begins with the
features offered by traditional analog partyline (PL) intercom user devices and adds
a range of new capabilities, along with the
advanced performance and flexibility that
Dante® audio-over-Ethernet provides. Over
a standard IP network, multiple Model 372A
and other compatible Studio Technologies’
beltpack units can be used to create partyline intercom applications with help from an
external Dante-enabled audio matrix such as
the Studio Technologies’ Model 5422 Dante
Intercom Audio Engine. Alternately, Model
372A units can be used “point-to-point” or
interfaced with Dante-compatible matrix
intercom systems.
Having one talk and two listen channels may
seem unconventional. But it can be ideal
for many “real-world” applications. Often
an intercom user is primarily listening and
non-verbally responding to requests made
by producers, directors, or stage managers.
Typically, the Model 372A will be configured
to be part of one talk-and-listen party-line
intercom channel. During the time that an
event is taking place the listen function will
serve a much more important role; the talk
function will rarely be utilized. However, the
second listen channel will often be important.
Typically, it will be designated as a programlisten or “show audio” channel. The two
listen channels, along with the ability to
receive and display call signals, allow the
Model 372A to very effectively support production personnel in a compact and costeffective manner.
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, talk button operation, and headphone
channel assignment. Features include
integrated sidetone, call signal receive
display, and remote mic kill (“talk off”). The
range of capabilities, along with the excellent
audio quality provided by the digital audio
signal path, offers a unique and powerful
user experience.
Setting up and configuring a Model 372A
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. The Model 372A is compatible with
both broadcast and “gaming” headsets.
Figure 1. Model 372A Intercom Beltpack top and bottom views
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MODEL 372A
INTERCOM BELTPACK
A broadcast or intercom-style headset with
a dynamic or electret (DC-powered) microphone can be interfaced with the Model 372A
using a 5-pin XLR connector. The Model
372A also directly supports connection of
earbuds or gaming headsets that utilize a
3.5 mm 4-conductor TRRS plug. These moderately priced devices, commonly associated
with mobile phones or personal computers,
are often of high-quality and may be preferred for some applications. With the Model
372A’s moderate price and ability to support
a broad range of headset devices the overall
cost of deploying an intercom system can
often meet budget goals.
The STcontroller software application is used
to select the unit’s operating parameters. The
talk pushbutton switch can be configured for
optimal operation. Two “push-in/push-out”
(“pop-out”) rotary controls make it easy to set
and maintain the desired headphone output
level. The Model 372A’s compact 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 372A 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 education and commercial
theater, sports and entertainment TV and
radio events, streaming broadcasts, corporate and government AV, post production,
and aerospace.
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 372A is AES67
compatible and compliant with the Dante
Domain Manager™ software application.
Two bi-color LEDs provide status indications
of the Dante interface. The Dante Identify
command takes on a unique role with the
Model 372A. Not only will it cause the talk
pushbutton’s orange LED to light in a highly
visible sequence, it will also turn off (“kill”)
the talk function if it is active.
Audio Quality
The Model 372A offers “pro” audio performance that is not found in typical party-line
(PL) intercom beltpacks. 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 as required. 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.
Dante Audio-over-Ethernet
Audio data is sent to and received from the
Model 372A using the Dante audio-overEthernet media networking technology. As a
Dante-compliant device, the Model 372A’s
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 372A’s
processor where channel routing, headphone
one audio output (Dante transmitter) channel
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MODEL 372A
INTERCOM BELTPACK
level control, and sidetone creation are
performed within the digital domain. This
provides flexibility, allowing precise control
of the audio signals and eliminating the need
for the two rotary level controls from having
to directly handle analog audio signals. The
audio signals destined for the 2-channel
headphone output are sent to a highperformance digital-to-analog converter
and then on to robust driver circuitry. High
signal levels can be provided to a variety
of headsets.
Call Function Receive
A call receive function allows Model 372A
users to be provided with a visual indication
that a call signal is active. The orange LED
within the pushbutton switch will first flash
then light solid whenever a call signal is detected on either of the Dante receiver (input)
channels. Using 20 kHz tones, the call signals are sent within the Dante audio channels
(“in band”) allowing interoperability between
multiple Studio Technologies’ beltpack units
as well as being compatible with legacy partyline intercom systems. Call signals can be
useful to indicate to users that they are needed “on headset” or should be actively listening to an intercom channel. The call function
can also be used to provide real-time cues to
production personnel during the running of
live events.
Configuration Flexibility
A highlight of the Model 372A 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 372A by way of an Ethernet network connection. Configurable parameters
include microphone power and preamplifier
gain, headphone monitoring, sidetone audio
operation, and talk button operation.
The microphone input can be selected for
compatibility with dynamic or electret (DCpowered) microphones. The gain of the
microphone preamplifier can be selected
from among five choices. These choices
allow compatibility with the variety of microphones that are part of broadcast, intercom,
and computer gaming headsets.
To support optimum user performance, the
Model 372A’s talk pushbutton switch can be
configured from among three choices: Push
to Talk, Latching, or Push to Talk/Tap to
Latch. Two audio channels arrive via Dante
receivers (inputs) and are destined for the
2-channel headphone output. Each input
source can be independently routed to the
left headphone channel, right headphone
channel, or both the left and right headphone
channels. This flexibility allows a variety of
listening environments to be created, including stereo, single-channel monaural, and
dual-channel monaural.
Ethernet Data and PoE
The Model 372A 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 high-reliability
environments. An LED displays the status
of the network connection.
The Model 372A’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
372A’s PoE interface reports to the power
sourcing equipment (PSE) that it’s a class 1
(very low power) device.
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