Clear-com SB-704 User Manual download pdf (Page 19)

SB-704 MAIN STATION

2-1

INSTALLATION

This chapter describes installation of the SB-704 in an intercom system.

INSTALLATION OVERVIEW

This section describes the Clear-Com concept in intercom line

interconnection under the following topics:

• Intercom Line Connection

• Line Termination

• Station Powering

• Cable Considerations

INTERCOM LINE CONNECTION

The SB-704 provides one male XLR-3 connector for each main intercom line

and ten male XLR-3 connectors for the separate assignable intercom

channels.

LINE TERMINATION

The fundamental concept of the Clear-Com party-line intercom is that all

stations provide high impedance into a single system termination.

Note: 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 SB-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 imbalance of hybrid null circuits.

Switching of the termination on and off on the SB-704 is with back-panel

switches. The SB-704 is shipped from the factory with all four lines

terminated.

USING THE LINK FUNCTION

The link function in the SB-704 uses relays to connect 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

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Clear-com SB-704 User Manual Page 19