Matrix: Should I enable the CCI-22 interface card PL line terminations?

Question:  I have installed a CCI-22 interface card on my Eclipse system over to a wired Clear-Com 2 channel party-line comm system.  Should I enable the CCI-22 card line terminations on the card or should I leave the terminations set on the wired party-line in place?

Answer:  Normally we recommend NOT to enable the termination on the CCI-22 card as the termination is normally provided by the unit  powering the partyline system.
To ensure correct operation of the external party-line, only one termination can be installed on any given party-line channel.  A party-line termination is normally provided by the component powering the party-line. Although the CCI-22 is not designed to supply power to an external party-line system, each channel of the CCI-22 features a Clear-Com termination circuit that can be connected to the party-line by installing a jumper. This termination network is not normally connected, and should only be connected in the rare case that the external party-line does not include a termination circuit.
If a party-line has more than one termination circuit, it will not null correctly. The most common symptom of this is when the line does not null, even though the “R” null control has been turned all the way counter-clockwise. If this happens, check all components connected to the party-line that are capable of providing a termination to be sure that only one termination is connected to the party-line. 
The two termination circuits on the CCI-22 connect to the channel A and B party-lines; they are enabled and disabled by the jumpers at JP100 (which controls the termination circuit for channel A) and JP200 (which controls the termination for channel B).  JP100 and JP200 are located near the center of the CCI-22 main circuit board as shown in the picture below. When either jumper is next to the label “B”, its termination is disabled; moving the jumper next to the label “A” enables the termination.


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