Clear-Com IF4W4 - Manual (Page 8)

I F 4 W 4 4 - C H A N N E L F O U R - W I R E I N T E R F A C E 1 - 2
four-wire input and output. The interface mounts in a standard 19 in. (48.64
cm) equipment rack and is 1.75 in. (4.48 cm) in height.
Figure 1-2: IF4W4 Rear View
Installation and setup requirements are the same for all channels of the IF4W4
interface (i.e., A, B, C, or D channels).
OPERATION
For normal operation, the position of the ‘Link’ switches on the front of the unit
do not change after installation. The only controls on the IF4W4 that require
adjustment on a day-to-day basis are the ‘In’ (receive) and ‘Out’ (transmit)
controls on the front of the unit.
NULL ADJUSTMENT
The ‘Null’ control eliminates most of the receive signal from the transmit signal.
This control should be adjusted at installation and when the party-line cable
configuration changes. For example, if the number of stations on the party line
or the length of the cable increases or decreases.
R, L and C controls provide line-length compensation for adjusting the null.
These controls allow nulling for Clear-Com Party Line cable runs from 400 to
4000 feet (122m to 1219m).
To Adjust the Null
1. Connect a TS1 earphone or a four pin XLR headset (for monitoring the test
tone provided with the interface) into the ‘Null Monitor’ connector on the
front panel.
2. Push the appropriate test null button for the channel to be nulled. A tone
will be audible to help null the circuit.
Note: Depending on the installation the initial tone could be very loud so it is
recommended the earphone or headset is not worn until the volume of
the tone has been reduced to a safe level.
3. Turn the R, L and C null control in either direction until a decrease in
audible tone is observed. Continue to adjust the controls until the tone has
become inaudible.
4. Make fine adjustments by going back a couple of times over the R, L and C
adjustments for a complete null.
If Complete Null Is Not Possible
1. Check for proper termination of the line.
Note: High frequency is controlled by line compensation. This part of the tone
is distinguishable by its buzzing sound.