Studio Technologies 45DC User Manual
Model 45DC
Dante™ to Dual Party-Line
Intercom Interface
User Guide
Issue 1, January 2015
This User Guide is applicable for serial numbers
M45DC-00151 and later with application firmware 2.2 and later
Copyright © 2015 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50017-0115, Issue 1
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Table of Contents
Introduction ................................................................... 5
Installation ..................................................................... 9
Configuration ................................................................ 12
Operation ...................................................................... 14
Technical Notes ............................................................. 19
Specifications ................................................................ 23
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Issue 1, January 2015 Model 45DC User Guide
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Introduction
The Model 45DC Dante™ to Dual Party-Line
Intercom Interface is designed for applications that utilize single-channel analog party-line (PL) intercom technology. The unit
provides two independent single-channel
interfaces that each support one party-line
audio channel. Single-channel party-line
intercom systems are commonly used in
theater, entertainment, and education applications where a simple, reliable, low-cost,
and easy to use solution is desired. Analog
party-line products from Clear-Com® and
ASL are directly compatible with the Model
45DC. The Dante Audio-over-Ethernet media networking technology is used to transport the send and receive audio channels
associated with each of the two party-line
circuits. Two hybrid circuits with automatic
nulling provide excellent audio quality and
high return-loss. (These hybrid circuits are
sometimes referred to as 2-wire to 4-wire
converters.) The Model 45DC is directly
compatible with the latest broadcast and
audio equipment that uses Dante technology. An Ethernet connection is all that’s
required to make the Model 45DC part of a
sophisticated, networked audio system.
A Model 45DC can interconnect with devices such as matrix intercom systems,
DSP processors, and audio consoles. The
Model 45DC is directly compatible with the
RTS ADAM® OMNEO® matrix intercom
network. Alternately, two Model 45DC units
can interconnect by way of the associated
Ethernet network. The Model 45DC can be
powered by Power-over-Ethernet (PoE) or
an external source of 12 volts DC. Two party-line power sources with impedance termination networks can be supplied by the
Model 45DC, allowing connection of two
sets of user beltpacks such as the ClearCom RS-501 and RS-701. A Model 45DC
Figure 1. Model 45DC standard “throw-down” front view
Figure 2. Model 45DC back view
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can also connect with one or two existing
powered and terminated intercom circuits.
Audio level meters provide confirmation
of system performance during setup and
operation. Support for transporting call
light signals between Model 45DC units is
also provided.
Standard connectors are used for partyline intercom, Ethernet, and DC power
interconnections. The Model 45DC’s
enclosure has a “1/2-rack” 1U form factor
and weighs less than two pounds, making
it well suited for use in portable applications. Alternately, using one of the optional
rack-mount front panels, one or two Model
45DC units can be mounted in a single
space (1U) of a standard 19-inch rack
enclosure.
Applications
There are two main ways that the Model
45DC can be used in applications. The
first is to add party-line intercom support
for matrix intercom systems. The second
is to link two stand-alone party-line intercom systems. Ports on matrix intercom
systems that support Dante, such as the
RTS ADAM with OMNEO, can be routed to
the Model 45DC’s Dante input (receiver)
and output (transmitter) channels. The
Model 45DC’s circuitry will then convert
these signals into two single-channel party-line intercom circuits. In this way adding
party-line support to RTS + OMNEO is a
simple task. The Model 45DC can also be
used with matrix intercom systems that
don’t support Dante. An external analogto-Dante interface can be used to convert
analog intercom ports to Dante channels.
Once in the digital domain, these Dante
channels can be interconnected with the
Model 45DC’s audio input and output
channels.
Two separate sets of party-line intercom
circuits can easily be interconnected using
two Model 45DC Interfaces. At each end
a Model 45DC is connected to one or two
party-line circuits as well as the Dante
network. The Dante Controller application will then be used to route the audio
channels between the two units. That’s
it — nothing else is required to achieve
excellent performance.
The Model 45DC can also be used to
“bridge” two single-channel party-line
intercom circuits with one 2-channel partyline intercom circuit. This involves using
a Model 45DC for the two single-channel
circuits and one of the Studio Technologies Model 45DR Intercom Interface units
for the 2-channel circuit. The Model 45DR
is the “cousin” of the Model 45DC and
supports one 2-channel party-line intercom circuit rather than two single-channel
circuits. These 2-channel circuits, typically
supported by equipment from RTS, are
commonly used in broadcast applications.
Party-Line Interfaces
The Model 45DC’s two party-line intercom
interfaces are optimized for connection
with two single-channel party-line circuits
and user devices such as those associated with equipment from Clear-Com. (While
the Model 45DC will function in a limited
manner with a 2-channel RTS TW circuit,
the Model 45DR Intercom Interface is the
much-preferred choice.) Each interface
has a party-line active detection function
to ensure that should a beltpack or active party-line circuit not be connected
the Model 45DC’s interface circuitry will
remain stable. This unique feature makes
certain that objectionable audio signals,
including oscillations and “squeals,” won’t
be sent to other Dante-enabled devices.
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A significant capability of the Model 45DC’s
two party-line intercom interfaces is their
ability to supply DC power and 200 ohm
AC terminations to “create” two independent intercom circuits. The 28 volt DC
output can power user devices such as
beltpacks. With up to 150 milliamperes
(mA) of current available, a typical entertainment application could connect up to
three RS-501 or five RS-701 beltpacks to
each of the Model 45DC’s two interfaces.
In many applications this can eliminate the
need for an external intercom power supply, thereby reducing total system cost,
weight, and required mounting space. The
power supply outputs are monitored for
over-current and short-circuit conditions.
Under firmware (embedded software)
control the outputs will automatically cycle
off and on to help prevent damage to the
circuitry and connected equipment.
Dante Audio-over-Ethernet
Audio data is sent to and from the Model
45DC using the Dante Audio-over-Ethernet
media networking technology. Audio
signals with a sample rate of 48 kHz and
a bit depth of up to 24 are supported.
Audio input (receiver) and output (transmitter) channels on associated Dante-enabled
devices can be assigned to the Model
45DC using the Dante Controller software
application. This makes selecting the way
in which a Model 45DC fits into a specific
application a simple matter.
Analog Hybrids with Auto
Nulling
Two circuits referred to as “hybrids” interface the Dante input and output channels
with the two party-line interface channels.
The hybrids provide low noise and distortion, good frequency response, and high
return-loss (“nulling”), even when presented
with a wide range of party-line conditions.
Unlike telephone-line (“POTS”) oriented
DSP-based hybrid circuits, the Model
45DC’s analog circuitry maintains extended
frequency response. With a passband of
100 Hz on the low end and 8 kHz on the
high end, natural-sounding voice signals
can be sent to and received from a partyline circuit.
The Model 45DC’s sophisticated hybrid
auto nulling function uses a combination
of digital and analog circuitry under microprocessor control to achieve significant
trans-hybrid loss. This return-loss “null” is
achieved by making a series of firmwaredirected adjustments to account for the resistive, inductive, and capacitive conditions
that are present on the connected party-line
cabling and user devices. Whenever one
of the Model 45DC’s auto null buttons is
pressed digital circuitry adjusts the associated hybrid to achieve its maximum returnloss in less than 15 seconds. While the
nulling process is automatic, it only takes
place upon user request. The resulting
null parameters are stored in non-volatile
memory.
Pro Audio Quality
The Model 45DC’s audio circuitry was designed in the spirit of professional
audio equipment rather than that found
in typical party-line intercom gear. High-performance components are used throughout, providing low-distortion, low-noise, and
high headroom. Using passive and active
filters the frequency response of the audio
channels is limited to nominally 100 Hz to
8 kHz. This range was selected to provide
excellent performance for human speech
while maximizing the ability of the hybrid
circuits to create substantial “nulls.”
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