Clear-Com HLI-FBS - Manual (Page 114)

3. Apply nulling to the connected channel on the CCI-22. To null the channel:
a. Insert the accessory earphone into the front-panel Test jack. A test tone, for all
frequencies, is produced every 0.5s.
b. While listening to the test tone, adjust the R (Resistance) control until the tone is at a
minimum.
c. Repeat Step b. for the L (Inductance) and C (Capacitance) controls. These controls
compensate for each component of the line’s impedance, providing the best possible null.
Because the R, L and C controls interact, you may have to adjust these controls several
times to minimize the test tone / achieve a deep null.
Note :
The null circuit on the CCI-22 is effective on line lengths between 0 - 4000 feet (1200m)
with impedances in the range of 120 to 350 ohms. Nulling can reduce local audio in the
received signal by < 30 dB over the 200 Hz - 8 kHz frequency range.
Tip: For more information on the CCI-22 nulling circuit, see the CCI-22 Manual.
4. If necessary, adjust the In / Out level controls on the CCI-22 (Send and Recv, located on the
front panel next to the R, L and C nulling controls).
Note:
The Send level control affects the level of the audio signals from the
Eclipse Matrix to the external party-line, and the Recv 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.
Tip: For more information about managing the HelixNet to Eclipse connection in ECS, see your ECS
documentation (including Help).
112 HelixNet Partyline User Guide