ANSI T1.628a-2001 pdf download ECS – Connection and Ring Back Addendum
6.2.8.2 Providing Ringback at a BRI/NT2 or PRINT2 Interface f the. network receives a Ringback request from the direction of the PSAP while in. the ECS Call Hold-Connected. service state, the network shall send a FACILITY message including a Facility information element coded with the ringbackRequest operation.
This FACILITY message shall use the call reference of the associated call on the ISDN interface. In addition. the network shall follow the procedures of T1.610-1998 for generating and sending the FACILITY message over the ISDN access. ECS Ringback is not supported in BRI/NT2 and PRI/NT2 interfaces when the NT2 does not support ECS Call Hold.
Thus if the network receives a Ringback request from the direction of the PSAP while in the ECS Call Hold- Held service state, the network discards the request. Support of the RingbackRequest operation by the NT2 on an ISDN BRI or PRI is optional. If the NT2 supports the RingbackRequest， it provides the. appropriate treatment towards the end-user depending_ on the connection status of the end-user. An NT2 that does not support the ringbackRequest operation follows the procedure of T1.610-1998 for handling unrecognized operation codes, i.e. returns a reject component coded “unrecognized operation.” The network should not consider receipt of such a reject component in response to a Ringback request to be an error condition.
6.2.8.3 PSAP Request for Ringback If the PSAP determines that it needs to request the network to invoke Ringback, then the procedures to be used depend on the type of interface to the network that is supported by the PSAP. If the PSAP supports an ISDN interface with stimulus protocols, then the PSAP uses the Feature Key Management procedures of T1.610-1998 to request Ringback. In this case, the PSAP shall send an INFORMATION message to the network including the Feature Activation information element with a Feature ldentifer assigned for Ringback Request. The call reference of the related call shall be used in this INFORMATION message.
Upon receipt of such an INFORMATION message, the network shall proceed to pass the ringback request towards the originating interface, if the ringback capabiity is supported (7.3.3). If the PSAP supports an. ISDN interface that uses functional protocols. .then, the PSAP uses the common information element procedures of T1.610-1998 to request Ringback. In this case, the PSAP shall send a FACILITY message to the network including a Facility information element coded with the ringbackRequest operation. This FACILITY message shall use the call reference of the associated call on the ISDN interface. In addition, the PSAP interface shall follow the procedures of