Avaya 03-300430 User Manual

For systems supporting Media Modules:
Analog CO trunks are 2-wire analog lines to the CO which support both incoming and outgoing 
calls. CO trunk MM711 Analog Media Modules have eight ports.

Note:

Although the CO-TRK MO is provided for G700 and G350 media gateways, this 
MO only partially supports the MM711 Analog Media Module.

The following sequences show the interactions between the switch and the CO during call setup 
for both loop-start and ground-start trunks.

Idle State: Tip = ground, Ring = CO Battery 

Outgoing Call:

1. PBX Off-Hook (Seize message): Closes the Tip-Ring Loop

CO response: DC loop current + Dial tone

2. PBX On-Hook (Drop message): Open Tip-Ring loop, no loop current

CO response: CO goes to idle state (see Note)

Incoming Call:

1. CO Applies Ringing Voltage

PBX response: Detect ringing current

2. PBX Off-Hook (Answer message): Close loop

CO response: Trip ringing, provide loop current

3. PBX On-Hook (Drop message): Open Tip-Ring loop, no loop current

CO response: CO goes to idle state 

Note:

CO does not normally provide an On-Hook (Disconnect) signal.  Exceptions to 
this rule include Netherlands loop start and UK loop-calling guarded-clearing.