Studio Technologies 45DC Datasheet

Key Features:

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Dante™ Audio-over-Ethernet technology

• Integrated party-line intercom power sources

• Analog hybrids with auto null capability

• Input and output level metering

• Excellent audio quality

45DC, allowing connection of user beltpacks such

as the Clear-Com RS-501 and RS-701. A Model

45DC can also connect with an existing powered

and terminated intercom circuit. Audio level meters

provide confirmation of system performance during

setup and operation. Standard connectors are used for party-line

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.

• PoE and 12 volt DC powering

• Standard connectors

• Table-top, portable, or optional rack-mount use

Overview

The Model 45DC Dante™ to Dual Party-Line Intercom Interface is

designed for applications that utilize single-channel analog party-

line (PL) intercom technology. This type of intercom is 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® are 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 equip-

ment 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 in-

tercom 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. A party-line power source and

impedance termination network can be supplied by the Model

Applications

There are two main ways that the Model 45DC can be used

in applications: adding party-line 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 45DC’s

Dante input and output channels. The Model 45DC’s circuitry

will then convert these signals into two single-channel party-line

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 analog-

to-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 circuits can easily be intercon

nected using two Model 45DC Interfaces. At each end a Model

45DC is connected to both party-line intercom 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 party-line intercom

circuit. This involves using a Model 45DC for the two single-

channel circuits and one of the Studio Technologies’ Model 45DR

Interface units for the 2-channel-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.

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Party-Line Interfaces

The Model 45DC’s two party-line interfaces are

optimized for connection with two single-channel

party-line intercom circuits such as those associ

ated with equipment from Clear-Com and other compatible manu

facturers. (While the Model 45DC will function in a limited manner

with a 2-channel RTS TW circuit, the Model 45DR Interface is the

much-preferred choice.) The Model 45DC’s party-line interfaces

can correctly function with powered (“wet”) or unpowered (“dry”)

party-line intercom circuits. 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-connected devices.

A significant capability of the Model 45DC’s two party-line

interfaces is their ability to supply DC power and 200 ohm AC

terminations to “create” an intercom circuit. The 20 volt DC

output can power user devices such as beltpacks. With up to

200 milliamperes of current available, a typical theater applica

tion could connect up to four RS-501 or six RS-701 beltpacks

for each of the Model 45DC’s two interfaces. In many applica

tions 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 software control

the outputs will automatically cycle off and on to help prevent

damage to the circuitry and connected equipment.

Note that a typical stand-alone party-line intercom power

supply will provide approximately 30 volts DC. And user beltpacks

from Clear-Com are specified to function correctly with as little

as 12 volts DC. This 18 volt difference allows support for long

cable runs and their associated DC voltage drop. But the Model

45DC’s two party-line intercom power supply circuits are limited

to what they can provide due to the energy available from the

connected PoE power source. In an effort to most efficiently

support connected user devices the DC voltage supplied by the

Model 45DC’s party-line intercom power supply circuitry was

selected to be 20 volts DC. This lower voltage then allowed

the very-reasonable 200 milliamperes of current to be supplied,

enough for supporting multiple user beltpacks. In conclusion,

while providing 20 volts DC for the two party-line intercom circuits

is somewhat non-standard, it should prove to be a reasonable

compromise. For the intended Model 45DC applications, limiting

the maximum length of the user-device interconnecting cabling

shouldn’t be an issue — the length limit should still be in the

hundreds of feet. And an external party-line intercom power

supply can always be used if the provided source is not sufficient

for a specific application.

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Dante Audio-over-Ethernet

Audio data is sent to and from the Model 45DC using the Dante

Audio-over-Ethernet media networking technology. For flexibility

in meeting application requirements bit depths of up to 24 and

sample rates of 44.1 and 48 kHz are supported. Audio input and

output channels on associated Dante-connected 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 party-line 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 software-directed ad

justments 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 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 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 head

room. 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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Studio Technologies, Inc. Model 45DC Intercom Interface, Issue 1, Page 2