Clear-Com TW-12C - Manual (Page 13)

S y s t e m I n s t a l l a t i o n M a n u a l
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6. Repeat steps 3, 4 and 5 until you obtain a complete null.
Note: If an almost-complete null cannot be obtained, chances are something is
wrong with the intercom line feeding that side:
• If the “R” control is fully counter-clockwise, the line has double terminations
or an excessive resistive load on it. If the “R” control is fully clockwise, then
the line has no termination.
• If the “L” control is fully turned in either direction, most likely there is a
problem in the intercom line connected to that side. When a Clear-Com
system is connected, the “L” control should be slightly off its center of travel.
The “L” control corrects for the low-frequency inductive and capacitive
elements that the intercom system presents to the line.
• If the “C” control is fully counter-clockwise, this indicates a very short line
(under ten feet) and can be ignored. If the “C” control is fully clockwise, this
indicates an excessively long line (over 5000 feet). The “C” control
compensates for cable capacitance.
Repeat steps 2 through 6 for the SYSTEM 2 side (press the Null Test button for
SYSTEM 2 and adjust the “R”, “L”, and “C” controls for that side).
Setup is now complete, and the TW-12C is ready to operate.
GAIN ADJUSTMENT
The GAIN adjustment pots allow a gain trim of +/- 4dB. The mid-pot position
is calibrated for a gain of 0dB. This is the nominal setting for normal operation.
If you prefer a small boost or cut in gain in either direction, this control allows
for it.
Caution: If you do not obtain a good null of the hybrid network, the system might
oscillate with some GAIN settings. With a good null of the hybrids, it is possible to
have +4 dB gain on both sides. If the system oscillates or tends to be unstable, perform
the Hybrid Null Adjustment procedure described above.