SIGNALLING SYSTEM DC5
This signalling system is used for signalling between a PBX and co-sited equipment. The system operates over two discrete signalling wires which are electrically separated from the associated speech circuit. The two signalling wires are known as E&M. DC signals are sent on the M wire and are received on the E wire. Although the system is often referred to as E&M signalling it should be noted that it is not compatible with some other forms of E&M systems.
The speech pair (pairs if 6 wire type) will terminate on a loop condition. The M wire will be disconnected when idle and earth when seized. The e wire has a 50v condition on it on idle.
To call the distant end an earth is presented to the m wire.
Testing a DC5 circuit
Last revised: December 18, 2010