Clear-Com RM-704 - Manual (Page 19)

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
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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.