Clear-Com MS-704 - Manual (Page 17)

M S - 7 0 4 / R M - 7 0 4 F O U R - C H A N N E L M A I N / R E M O T E S T A T I O N S
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INSTALLATION
This chapter discusses how to install the MS-704 and RM-704 intercom stations
in an intercom system.
INSTALLATION OVERVIEW
This section describes the Clear-Com concept of intercom line interconnection.
The following subjects are discussed:
• Intercom line connection
• Line termination
• Station powering
• Cable considerations
Intercom Line Connection
The MS-704 provides two male XLR-3 connectors for each intercom line.
The RM-704 provides a male and female XLR-3 connector for each intercom
line, which are looped through.
Line Termination
The fundamental concept of the Clear-Com party-line intercom is that all
stations provide high impedance into a single 200-ohm system termination.
CAUTION: An intercom line must be terminated. Care must be taken not to
“double”-terminate a line. All unused intercom inputs must be
terminated to keep the line drive circuits stable.
The MS-704 provides switchable terminations of the intercom lines. 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 imbalance of hybrid null networks.
A double- or multiple-terminated line will cause low levels and severe unbalance
of hybrid null circuits.
Switching of the termination on and off on the MS-704 is with back panel
switches. The MS-704 is shipped from the factory with all four lines terminated.
USING THE LINK FUNCTION: The link function in the MS-704 connects
the four party lines together. In doing so, it also removes the terminations from
channels B, C, and D such that the new party line on channel A has only one
termination when link is activated. If there is more than one MS-704 in a system,
the link function can only be used at the station where the terminations are set
on.
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