Clear-Com ENCORE RM-702, Инструкция по эксплуатации

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R M - 7 0 2 T W O - C H A N N E L R E M O T E
2 - 3
The RM-702 unit is shipped with the jumper plug over pins 2 and 3 to
maintain the power-channel isolation. Power-channel isolation ensures
that if one channel loses power, the other channel will continue to operate.
5. Replace the cover of the RM-702.
LINE TERMINATION
The fundamental concept of Clear-Com party-line intercom is that all stations
provide high-impedance current-sourced signals into a single common system
termination.
The receive or listen section of stations contain a hybrid null circuit that
attempts to reject (null) any talk signal being sent by that station on that
channel. The hybrid null circuit depends on a known impedance on the
intercom line to accomplish this. Variations in impedance on the line upset the
null .
CAUTION:All Clear-Com Intercom lines must be terminated. Care must be
taken not to fail to terminate or to “double”-terminate a line.
All unused intercom inputs must be terminated to keep the line
drive circuits stable.
The RM-702 does not provide termination on the intercom line. Clear-Com
main stations and power supplies provide switch-selectable termination
networks on all intercom output lines. It is up to the user to determine where
the termination will be provided. An unterminated line will cause excessive
levels, possible oscillation of line drivers, and severe unbalance of hybrid null
networks. A double- or multiple-terminated line will cause low levels and
severe unbalance of hybrid null circuits.
The termination of an intercom line (or channel) is a 220 Ohm resistor in
series with a 4.7 K Ohm that is paralleled with a 10 uF capacitor.
STATION POWERING
Typical Clear-Com systems are powered by a main station or a power supply.
Clear-Com power supplies can be paralleled to increase the number of remote
stations that can be operated in a system.
CABLE CONSIDERATIONS
The Clear-Com intercom line is intended to run on a shielded twisted pair of
cable per channel of intercom. One conductor carries full duplex (“two-way”)
audio, the other conductor carries the DC power for remote stations. The
shield is used for ground return for audio and power. When choosing
interconnect cable, keep the following considerations in mind:
• DC resistance of the ground or common conductor affects crosstalk. For
runs longer than 500 ft. (152.5 m), do not use wire smaller than 20 gauge.