Services Supported by DIOD Trunks

Direct inward and outward dial (DIOD) trunks are 2-wire analog lines to the CO which support the following services:

• Both incoming and outgoing CO calls
• DID trunk
• DID trunk and 1-way outgoing DIOD

MM711 trunk Media Modules provide eight ports for loop-start CO trunks.

Loop Start Operation

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 (see Note).

Direct Inward Dialing (DID)

1. CO Applies Ringing Voltage.
1. PBX Response: Detect ringing current and close loop.
2. CO Response: Send DTMF digits.
3. PBX Response: Acknowledge of Number dialed and open loop.
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 (see Note).

   Note:

   CO does not normally provide an On-Hook (Disconnect) signal.