Clear-Com EF-701M - Manual (Page 31)

E F - 7 0 1 M I N T E R F A C E 2 - 9
Troubleshooting Tips for Nulling
• If the “R” control is turned fully counterclockwise, the line has multiple terminations or
a resistive load.
• If the “R” control is fully clockwise, then the line is unterminated.
• 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. With a Clear-Com party line
connected, the “L” should be slightly to either side of the mid-pot position.
• The “C” control compensates for cable capacitance and is line-length dependent. If fully
counterclockwise, this indicates a very short line (<10 feet or < 3 m). This is a valid
setting for a short line.
• If “C” is fully clockwise, this indicates an excessively long line (>4000 feet or >1200 m).
• Remember, you are adjusting the null to/from the local party-line system. Only the
transmit send level at the local EF-701M will affect the listen receive level at the remote
EF-701M.