Nortel Circuit Card Installation Manual page 642

Page 642 of 906
Figure 148
Signaling orientation for tandem connection between E&M and CO trunks
Far end PBX
Tie trunk
553-3001-211 Standard 3.00
NT8D15 E&M Trunk card
Outgoing
Incoming
E&M
Idle state
For E&M signaling, in the idle state the M lead is ground and the E lead is an
open circuit.
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).
August 2005
Near end PBX
(senderized)
CO/FX/
WATS
PBX-CO trunk
553-6262
CO