Clear-Com CCI-22 - Manual (Page 9)

Vitec Group Communications
CCI-22 Dual Channel Party-Line Interface Instruction Manual 1 - 3
2. Plug the accessory earphone into the front panel jack labeled "Test".
This will disconnect the interface from the matrix and enable the test
oscillator. The oscillator produces a square wave with both low and
high harmonics, allowing you to test all frequencies. The test tone
pulses approximately every half-second.
3. While listening to the test tone in the earphone, adjust the "R"
control until the tone is at a minimum.
4. Repeat Step 3 with the "L" and "C" controls. Because these controls
interact with each other, you will need to repeat steps 3 and 4
several times before you will have minimized the test tone. Continue
adjustment until the tone is virtually inaudible. If an almost complete
null cannot be obtained, it is likely that something is wrong either
with the wiring in the external party-line, or with one of the other
devices attached to the external party-line. Steps 5 through 9 are
troubleshooting hints.
5. If the "R" control is turned fully counter-clockwise, the line has either
more than one termination, or an excessive resistive load.
6. If the "R" control is fully clockwise, then the line has no termination.
7. The "L" control compensates for the low-frequency inductive and
capacitive elements of the external party-line. If the "L" control is
fully turned in either direction, it is likely that there is a problem in the
external party-line. When a Clear-Com party-line is connected, the
"L" control should be just to one side of its mid-pot position.
8. The "C" control compensates for cable capacitance; the setting
depends on the length of the line. If the "C" control is fully
counter-clockwise, this indicates a very short line (under ten feet);
this is a valid setting for a short line.
9. If the "C" control is fully clockwise, this indicates an excessively long
line (over 4,000 feet or 1200m).