Alpha Communications VM25WH Series Installation And Use Instructions Manual page 5

General Monitor Mounting and Wiring Information
Note: There are Black and Red pigtail wires coming from
terminals 'O' and 'LL' on the VH250E (or VH250P) P.C.
Board. The Black 'O' wire must jump to terminal 'O' on
the handset and the Red 'LL' wire must jump to terminal
'S' on the handset or the monitor will not activate when
the handset is signalled from the entrance station(s).
ON
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