# Tandem Trunking

## Description

Trunk circuits originating from one CO or system and terminating on another (tandem trunking) can be transparently interconnected without attendant intervention.

Tandem Trunking is dependent upon regulatory provisions imposed by the local telephone authority. This feature provides:

- answer supervision

- alternative routing

- interconnect restriction tables

- feature availability by Direct In Line (DIL) trunks

- incoming digit modification

- outgoing digit modification

- dial tone detection

- outpulsing arrangements

- variants in types of trunk circuit.

## Conditions and Feature Interactions

- Set the Public Trunk COS option to "Yes" in the Class of Service Options form if the trunk will be connected to the public network. This does not affect CO, Digital CO, LS/GS, DID, DASS CO/DID, DASS CO (outgoing only), or ISDN trunks which are already recognized as public network trunks by the system.

- When the Public Trunk COS option is used in conjunction with the Public Network to Public Network Connection Allowed COS option (set to "No"), users are prevented from dropping out of conferences that use two or more of these trunks.

- Trunks with the Public Trunk COS option set to "Yes" are identified as CO trunks when used in a conference or MSDN/DPNSS network; it does not apply to rerouting functions.

## Programming

1. Class of Service Options form

- Create a new COS by Setting the Public Trunk option to "Yes" (for users restricted from making public trunk to public trunk connections, ensure their Public Network to Public Network Connection Allowed COS option is set to "No").

2. Trunk Attributes form

- Assign the COS to the trunks.

3. Program the following forms:

- ARS Node Identities

- Call Rerouting

- Interconnect Restriction

- Intercept Handling

## Device Support

Not applicable

## Operation

None