Clear-Com CCI-22 - Manual (Page 8)

Vitec Group Communications
CCI-22 Dual Channel Party-Line Interface Instruction Manual
1 - 2
OPERATION
In normal use, the CCI-22 interface does not require operator
interaction. The front panel features a set of level controls and a
power indicator LED. The front panel also includes a set of three "null"
adjustment controls. The null adjustment controls are discussed in
“Installation”, Chapter 2.
LEVEL CONTROLS
The Send level controls affect the level of the audio signals from the
matrix to the external party-line, and the Recv ("receive") control
affects the level of the audio from the party-line into the matrix.
The Send and Receive controls have a range of ± 13 dB. They are
normally set at the center position when used with Clear-Com PL-Pro
or Encore party-line equipment.
POWER LED
The green Power LED lights when DC power is supplied to the
interface. The interface is powered by the party-line it is connected to.
Send and Return Rejection Null Adjustment
Normally this adjustment is made once during installation. If additional
adjustment is required use the following procedure.
A lack of 2-wire rejection will affect the sound of the operator's own
voice in his or her headset. In interfaces, it is necessary to "null"
(minimize) the rejection when an external party-line is placed in the
matrix environment. Ideally, there should be no portion of the T
alk
signal in the L isten signal. The nulling procedure for each channel of
the CCI-22 is described here.
The CCI-22 includes built-in nulling circuitry, including a test tone
generator and an accessory earphone. The earphone plugs into a
1/8-inch (3.1mm) phone jack on the front panel. When the earphone is
plugged in, it automatically switches on a test tone, and monitors the
output of the null circuit.
Separate "R" (Resistance), "L" (Inductance), and "C" (Capacitance)
controls compensate for each component of the line's impedance,
providing the best null possible.
The null circuit is effective on line lengths between zero and 4000 feet
(1200m) with impedances in the range of 120 to 350 ohms, and can
reduce local audio in the received signal by more than 30 dB over the
frequency range of 200 Hz to 8 kHz.
To null one channel of the CCI-22:
1. Connect the external party-line devices together with the cables they
are going to use to the CCI-22 channel.
Power
Send
Recv C
L
R
Test Null
PL