Clear-Com MS-704 - Manual (Page 14)

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 1 - 8
• LINE LENGTH: Four DIP switches (one for each channel) allow the
optimization of the nulling circuitry for each channel. The default (up
position) is for lines less than 400 ft. (122 m). The down position is for lines
longer than 400 ft. (122 m).
Hidden Adjustment Controls
Various adjustments are available beneath the front access panel.
• PANEL MIC GAIN: This control trims the panel microphone preamplifier
gain to compensate for different uses of the station.
The unit is shipped from the factory in the minimum gain position (fully
counter-clockwise). This level matches the headset microphone level when
the panel microphone is worked up close. Raising the gain from the factory
setting should be done carefully, as too much gain will increase the back-
ground noise in the intercom making it unusable.
• CHANNEL NULL ADJUST: The screwdriver-adjustable control beneath
each talk pushbutton marked null allows nulling of the hybrid circuitry
associated with each listen channel.
The amount of null in the listen circuitry varies with the length of the inter-
com line. Adding or removing stations and intercom cable will change the
null. For optimum performance, the null control will need to be adjusted
each time there is some change in the intercom line wiring.
If a panel microphone and speaker is being used, the setting of the null con-
trol is critical to prevent feedback.
To adjust the null control on a given channel:
1. Turn the sidetone adjust control just below the headset connector to
minimum.
2. Set a talk to the channel to be adjusted or send some program to the
channel and adjust the null control for the channel for minimum level in
the headphone. If the headset microphone is being used, hum or gently
scratch it for a continuous signal source to null on. If a good null is not
attainable, switch the long/short DIP switch for the channel (to the far
right of the hidden adjustments) to its opposite setting. Use the setting
that produces the best results.
3. Repeat the adjustment for all four channels on the station.
4. Adjust the sidetone adjust control for the desired amount of sidetone in
the headset.
• CHANNEL PROGRAM FEED LEVEL: Beside the null control for each
channel there is a control marked PGM, which adjusts the amount of
program being sent to that channel.
Each channel has two program sources:
1. The main program that is input from the rear panel XLR connector may
be enabled for a given channel with the program on/off DIP switches for
the channel.