Data Sheet

The Model 47 is designed to interface 2-wire full-duplex party-
line intercom circuits with 4-wire audio circuits associated
with matrix intercom systems. Other specialized audio system
interfacing applications can also be supported. The Model 47
provides two independent full-featured 2-channel interfaces.
Each interface contains two hybrid circuits which include
automatic 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 belt packs
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 47 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 47 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
• Dual-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 47’s 2-wire interfaces are optimized for direct con-
nection with dual-channel party-line (PL) intercom circuits. In
addition, single-channel party-line intercom circuits can also be
connected. Many broadcast applications use the dual-channel
TW-series from RTS®, including their popular BP325 belt pack.
Other industry-standard single- and dual-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 47’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 47’s 2-wire interfaces can correctly function with
powered (“wet”) or unpowered (“dry”) intercom circuits.
Powered 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 belt packs. In this type of application the
Model 47 is configured to operate in its external 2-wire power
source mode. In this mode the Model 47’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 47’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 47’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 47’s internal 2-wire power
source mode, the 30 volt outputs can power devices such as
50114-0810, Issue 2