Avaya Nortel Communication Server 1000 Reference page 443

Outgoing calls
Outgoing calls are processed as follows:
The M lead changes from ground to battery.
If answer supervision is provided by the far end, there is a change from open to ground
on the E lead (ground detection).
Figure 140: E and M Type I signaling patterns - originating party release
Circuit Card Reference
Operation
July 2011 443