Avaya DEFINITY Server CSI Maintenance Manual page 1057

DIOD-TRK (DIOD Trunk)
Loop start operation
Idle State - Tip = ground, Ring = CO Battery
A. Outgoing Call
1. PBX Off-Hook (Seize Message): Closes the Tip-Ring Loop
a. CO Response: DC loop current + Dial tone
2. PBX On-Hook (Drop Message): Open Tip-Ring loop, no loop current
a. CO Response: CO goes to idle state (see Note)
B. Incoming Call
1. CO Applies Ringing Voltage
a. PBX Response: Detect ringing current
2. PBX Off-Hook (Answer Message): Close loop
a. CO Response: Trip ringing, provide loop current
3. PBX On-Hook (Drop Message): Open Tip-Ring loop, no loop current
a. CO Response: CO goes to idle state (see Note)
C. Direct Inward Dialing (DID)
1. CO Applies Ringing Voltage
a. PBX Response: Detect ringing current and close loop
b. CO Response: Send DTMF digits
c. PBX Response: Acknowledge of Number dialed and open loop
2. PBX Off-Hook (Answer Message): Close loop
a. CO Response: Trip ringing, provide loop current
3. PBX On-Hook (Drop Message): Open Tip-Ring loop, no loop current
a. CO Response: CO goes to idle state (see Note)
NOTE:
CO does not normally provide an On-Hook (Disconnect) signal.
555-233-119 Issue 5 October 2002
1057