Studio Technologies 45DR User's Guide
User Guide
Issue 1, September 2014
This User Guide is applicable for serial numbers
M45DR-00151 and later
Copyright © 2014 by Studio Technologies, Inc., all rights reserved
www.studio-tech.com
50015-0914, Issue 1
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Table of Contents
Introduction ................................................................... 5
Installation ..................................................................... 9
Configuration ................................................................ 12
Operation ...................................................................... 13
Technical Notes ............................................................. 18
Specifications ................................................................ 21
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Introduction
The Model 45DR Dante™ to 2-Channel
Party-Line Intercom Interface is designed
for applications that utilize 2-channel analog party-line (PL) intercom technology.
This type of intercom is commonly used
in broadcast, corporate, and commercial
applications where a simple, reliable, easy
to use solution is desired. The RTS® TWSeries of 2-channel intercom equipment is
directly compatible with the Model 45DR.
The Dante Audio-over-Ethernet media
networking technology is used to transport the two send and two receive audio
channels associated with the party-line
circuit. 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 45DR is compatible with the latest broadcast and audio
equipment that uses Dante technology. An
Ethernet connection is all that’s required
to make the Model 45DR part of a sophisticated, networked audio system.
A Model 45DR can interconnect with
devices such as matrix intercom systems,
DSP processors, and audio consoles. The
Model 45DR is directly compatible with the
RTS ADAM® OMNEO® matrix intercom
network. Alternately, two Model 45DR units
can interconnect by way of the associated
Ethernet network. The Model 45DR can
be powered by Power-over-Ethernet (PoE)
or an external source of 12 volts DC. A
party-line power source and impedance
termination networks can be supplied by
the Model 45DR, allowing connection of
user beltpacks such as the popular RTS
BP325. A Model 45DR can also connect
with an existing powered and terminated
intercom circuit. Audio level meters provide confirmation of system performance
Figure 1. Model 45DR standard “throw-down” front view
Figure 2. Model 45DR back view
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during setup and operation. Standard connectors are used for party-line intercom,
Ethernet, and DC power interconnections.
The Model 45DR’s enclosure has a “1/2rack” 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 45DR 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
45DR can be used in applications: adding
party-line intercom support for matrix intercom systems and linking two stand-alone
party-line intercom circuits. Ports on matrix
intercom systems that support Dante, such
as the RTS ADAM with OMNEO, can be
routed to the Model 45DR’s Dante input
(receiver) and output (transmitter) channels. The Model 45DR’s circuitry will then
convert these signals into a 2-channel
party-line intercom circuit. In this way adding party-line support to RTS + OMNEO is
a simple task. The Model 45DR 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 45DR’s audio input and output
channels.
Two separate party-line intercom circuits
can easily be interconnected using two
Model 45DR Interfaces. A Model 45DR is
connected to each party-line circuit as well
as the Dante network. The Dante Controller software 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 45DR can also be used to
“bridge” a 2-channel party-line intercom
circuit with one or two single-channel
party-line intercom circuits. This involves
using a Model 45DR with the 2-channel
circuit and one or two of the Studio Technologies Model 45DC Intercom Interface
units with the single-channel circuits. The
Model 45DC is the “cousin” of the Model
45DR and supports two single-channel
party-line intercom circuits rather than one
2-channel circuit. These single-channel
circuits, typically supported by equipment
from Clear-Com®, are commonly used in
theatrical and entertainment applications.
Party-Line Interface
The Model 45DR’s party-line intercom
interface is optimized for connection with
2-channel party-line intercom circuits and
user devices such as the TW-Series from
RTS. In addition, other industry-standard
single- and 2-channel party-line intercom
circuits and user devices, including those
from Clear-Com®, are compatible. (While
the Model 45DR will function in a limited
manner with single-channel Clear-Com
circuits, the Model 45DC Intercom Interface is the much-preferred choice for
that.) A party-line active detection function
ensures that should a user beltpack or
active party-line circuit not be connected
the Model 45DR’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.
A significant capability of the Model
45DR’s party-line interface is its ability
to supply DC power and 200 ohm AC
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terminations to “create” an intercom circuit.
The 29 volt output can power a moderate
number of devices such as beltpacks. With
up to 240 milliamperes (mA) of current
available, a typical broadcast application
which uses two or three BP325 beltpacks
can be supported. In many applications
this can eliminate the need for an external intercom power supply, reducing total
system cost, weight, and required mounting space. The power supply output is
monitored for over-current and short-circuit
conditions. Under software control the
output 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
45DR 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
45DR using the Dante Controller application. This makes it simple to select the way
in which a Model 45DR fits into a specific
application.
Analog Hybrids with Auto
Nulling
Circuits referred to as “hybrids” interface
the Dante input and output channels with
the two party-line 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 DSPbased hybrid circuits, the Model 45DR’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 45DR’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 softwaredirected adjustments to account for the
resistive, inductive, and capacitive conditions that are present on the connected
party-line cabling and user devices. Whenever the Model 45DR’s auto null button is
pressed, digital circuitry adjusts the hybrids
to achieve their maximum return-loss 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 45DR’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 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.” Moreover,
the Model 45DR’s party-line intercom
power source offers a unique level of
performance; its ability to deliver power
while maintaining audio quality is simply
unmatched.
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