Datasheet

ManualsBrandsSTUDIO TECHNOLOGIES ManualsAncillary Studio & Broadcast ProductsModel 47A - Dual 2-Wire Analogue Audio to 4-Wire Analogue Audio Interface

The Model 47A is designed to interface 2-wire full-duplex party-

line (PL) intercom circuits with 4-wire audio circuits associated

with matrix intercom systems. Other specialized audio system

interfacing applications can also be supported. The Model 47A

provides two independent full-featured 2-channel interfaces.

Each interface contains two hybrid circuits which include au

tomatic nulling capability. The analog circuitry, under software

control, provides excellent audio quality and high return-loss. The

interfaces are compatible with powered and unpowered 2-wire

party-line circuits. They are capable of supplying DC power to

devices such as user beltpacks and user stations. Independent

power sources are provided for both channels (pins 2 and 3)

of each interface, allowing direct support for broadcast source

assignment panel (SAP) applications. Configuration settings

allow the 2-wire and 4-wire interface circuitry to be compatible

with a range of nominal signal levels. Audio level meters provide

user confirmation of system performance during setup and

operation. Applications for the Model 47A include mobile and

fixed television facilities, theme park and theater installations,

and industrial testing environments. Standard audio connectors

are used for all input and output signals. The Model 47A mounts

in one space (1U) of a standard 19-inch rack enclosure and

requires 100-240 volts, 50/60 Hz for operation.

• Two 2-channel party-line intercom interfaces

• Four analog hybrids with auto null capability

• Input and output level metering

• Excellent audio quality

• 2-channel intercom power sources

• Direct support for broadcast SAP panel applications

• Standard audio connectors

• Universal input mains powered

Highlights

Dual 2-Wire Analog Audio to 4-Wire Analog Audio Interface

2-Wire Interfaces

The Model 47A’s 2-wire interfaces are optimized for direct

connection with 2-channel party-line intercom circuits. In

addition, single-channel party-line intercom circuits can also

be connected. Many broadcast applications use the 2-channel

TW-Series from RTS®, including their popular BP325 beltpack.

Other industry-standard single- and 2-channel PL intercom

systems, including those from Clear-Com®, are also directly

compatible. To provide optimal signal matching and interface

performance the nominal level of the Model 47A’s 2-wire inter-

faces can be selected. Using DIP switches, accessible on the

front panel, the nominal levels can be selected to be either –10

or –14 dBu, settings that should allow compatibility with virtually

all party-line systems.

The Model 47A’s 2-wire interfaces can correctly function with

powered (“wet”) or unpowered (“dry”) intercom circuits. Pow

ered circuits have a DC voltage present, typically provided by

power supplies such as the RTS PS20. This DC power, nor

mally 30-32 volts, provides energy for connected devices such

as user stations or beltpacks. In this type of application the

Model 47A is configured to operate in its external 2-wire power

source mode. In this mode the Model 47A’s circuitry maintains

the required high-impedance load and, as in all cases, draws

no power from the party-line circuit. An auto-terminate func

tion ensures that should a “wet” circuit not be connected, the

Model 47A’s interface circuitry will remain stable. This unique

feature makes certain that objectionable audio signals, includ

ing oscillations and “squeals,” will infrequently be sent to the

connected 4-wire device.

A significant capability of the Model 47A’s 2-wire interfaces is

their ability to supply DC power and 200 ohm AC termination

to both channels (pins 2 and 3) of the connected intercom

circuits. Referred to as the Model 47A’s internal 2-wire power

source mode, the 30 volt outputs can power devices such as

50118-0914 Issue 1

Summary of content (4 pages)

PAGE 1
Dual 2-Wire Analog Audio to 4-Wire Analog Audio Interface Highlights • Two 2-channel party-line intercom interfaces 2-Wire Interfaces The Model 47A’s 2-wire interfaces are optimized for direct connection with 2-channel party-line intercom circuits. In • Four analog hybrids with auto null capability addition, single-channel party-line intercom circuits can also • Input and output level metering be connected.
PAGE 2
user stations and beltpacks. With independent power sources quantity of cable, the connected user devices, and the intercom provided for both pins 2 and 3 of each interface, applications power source. that include flexible party-line intercom channel routing will be Whenever a user presses one of the Model 47A’s auto null but- directly supported. As such, in applications that include both source assignment panel (SAP) and Model 47A units the need for external intercom power supplies can be eliminated.
PAGE 3
confirm that the nominal level DIP switch settings have been press and release) of the auto null button will begin the auto null properly made. During normal operation the meters offer rapid process for channel 1. Two taps of the button will begin the auto confirmation of audio signal flow in and out of the unit. Additional null process for channel 2.
PAGE 4
time can be better spent elsewhere!) The need to adjust trim turned out that in many applications only a small number of user potentiometers, fabricate special cabling and connector straps, devices, such as beltpacks, are typically connected to 2-wire use nulling earpieces, etc., had to be eliminated. For example, party-line intercom circuits.