EFJohnson 3000 SERIES - Manual (Page 195)

24-1
INTERCOM
SECTION 24 INTERCOM
24.1 DESCRIPTION
The intercom functions as an interface between
the Switch and remote base station to aid in alignment
of the system. The intercom allows technicians to
communicate between the Switch and remote base
station over one line pair while aligning a second pair.
Then the lines are switched to align the first pair.
24.2 INSTALLATION
24.2.1 EQUIPMENT REQUIRED
1. Audio Oscillator, 600 ohm output
2. AC Voltmeter, HP400E or equivalent
24.2.2 INSTALLATION PROCEDURE
1. Insert the Switch Intercom in an open slot in a card
rack. Shelf-1, Slot-3 is preferred.
2. Insert a 1 kHz tone at 0 dBm into the Rx portion of
J702.
3. Verify 0 dBm
±
1 dB at U701, pin 7.
4. Insert the speaker/microphone in jacks J701 and
J702.
5. Adjust R704 for maximum level out. (8V P-P across
speaker jack J701).
6. Remove the tone.
7. Speak into the microphone in a normal voice and
adjust R712 for -12 dBm
±
3 dB at U703, pin 1.
8. Use the patch cord cables supplied in the installa-
tion kit to patch from the Intercom RX to RX jacks
to the transmit and receive jacks on the selected
module (CIM). (Refer to VTM component layout.)
9. Adjust the volume knob on the front panel to the
desired listening level.
NOTE: J703 can be jumpered on pins 1 and 2 to pro-
vide a 600 ohm load to the receiving line. The jumper
may be placed on one pin only to provide a high
impedance bridging input (refer to the component lay-
out).