Technical information

Troubleshooting and Repair
75
Ground Start Trunk
The Ground Start Trunk serves most PBX-CO connections in an analog
environment.
Figure 14: Ground Start Trunk
Table 7: Ground Start Trunk Summary
Signal
Ground Start Trunk PBX
Outgoing
Ground Start Trunk
PBX Incoming
Seize
Ring lead goes active. PBX
grounds the ring lead
Tip lead goes active;
90 Vac is applied to
Ring lead in 2 sec on,
4 sec off cadence
Seize
Acknowledgment
Tip lead goes active; Audi-
ble Dial Tone generated;
ground returned on tip
Tip-Ring leads acti-
vated (shorted); Loop
Current flows in line
(Sheet 1 of 2)