Avaya 03-300430 User Manual

Idle state: Tip = open, Ring = CO Battery 

Outgoing Call:

1. PBX Off-Hook (Seize message): Places ground on Ring

CO response: Places ground on Tip

PBX response: Close the loop

CO response: Provide loop current

PBX response: Dial out digits

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

CO response: Open circuit on Tip

3. CO On-Hook first (Disconnect): Open circuit on Tip, no loop current

PBX response: Open Tip-Ring loop

Incoming Call:

1. CO Off-Hook (Seizure): CO applies ground on Tip and applies ringing voltage to the Ring 

lead.

PBX response: Make trunk busy for outgoing calls

2. CO Ringing: CO applies ringing voltage to the Ring lead.

PBX response: Detect ringing, ring destination (Attendant, hunt group, etc.)

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

CO response: Trip ringing, provide loop current

4. PBX On-Hook first (Drop message): Open the Tip-Ring Loop, no loop current

CO response: Open circuit on Tip

5. CO On-Hook first (Disconnect): Open circuit on Tip, no loop current