Clear-Com PS-704 - Manual (Page 16)

P S - 7 0 4 F O U R - C H A N N E L P O W E R S U P P L Y 2 - 2
LINE TERMINATION (REAR PANEL)
Switching of the channels’ terminations on and off are done with the
rear-panel toggle switches. In most systems, all terminations on the PS-704
should be in the on position (default setting). The fundamental concept of
Clear-Com party-line intercom is that all channels are terminated in one
location, preferably at the power supply.
Caution: All intercom lines must be terminated. Care must be taken not to
“double-terminate” a line. All unused intercom lines must also be
terminated.
The PS-704 provides terminations for each of its four channels. Clear-Com
main stations and power supplies provide switch-selectable termination
networks on all intercom lines. It is up to the user to ensure that the
terminations are set correctly. An unterminated line will cause excessive
levels, possible oscillation of line drivers, and severe imbalance of hybrid null
networks. A line with double or multiple terminations will cause low levels
and severe imbalance of hybrid null circuits.
If the PS-704 is the only power supply in the system (no other power supplies
or powered main stations are in the system) the termination switch on each
channel of the PS-704 should be switched to on. Simply toggle the rear-panel
switch labeled term to the on position. The termination switch should be set to
the off position only if the channel is terminated at another station.
PROGRAM INPUT (REAR PANEL)
A 3-pin XLR female connector provides the main program input to the
station. This input level is controlled by the rear-panel program level control
adjacent to the program in connector. This control sets the overall level for all
the channels. The input accepts a balanced or unbalanced line-level audio
signal. The program can be fed to any or all of the intercom lines by using the
front-panel toggle switches labeled program on/off. There is one of these
switches for each channel.
The pinout of the program input connector is as follows:
Pin #1 --- Ground (shield)
Pin #2 --- + Signal
Pin #3 --- - Signal
RACK MOUNTING
The unit requires 1.75 in. (44 mm or 1RU) of rack space. It requires no
additional free rack space above or below it for ventilation. The station is 7.5
in. (165 mm) in depth and requires at least 2.5 in. (64 mm) clearance in the
rear for connectors and cables. The single-piece front panel has integral “rack
ears.” This adds stability and strength.