AT&T 555-230-520 manual

Detailed Call Flow for Converse—VRI Calls

The CONVERSANT VRU offers a built-in external function called

‘‘converse_data.’’This function allows applications developers to perform this operation in a convenient and robust fashion.

To ensure the robust operation of the VRU data return operation, be sure to follow these recommendations:

■Set the analog flash timing to 600 msecs

■Ensure DTMF tones last at least 70 msec

■Ensure interdigit pauses last at least 50 msec

■(CONVERSANT only) Use the ‘‘converse_da’’t external function to return data to DEFINITY

For applications involving VRUs other than CONVERSANT VRUs, be sure to follow these recommendations:

■After the flash, ensure the VRU performs dialtone detection (stutter dialtone) for five seconds before outpulsing the converse data return feature access code.

■If no dialtone is received before the timeout, ensure the VRU does two more retries of the analog flash. Also, if no dialtone is detected after two retries, ensure the VRU logs an error.

■Whenever dialtone is detected, ensure the digits of the converse data return feature access code are outpulsed.

■After the converse data return feature access code is outpulsed, ensure the VRU performs dialtone detection (steady dialtone) again for five seconds before outpulsing the returned digits. If no dialtone is detected, ensure an error is logged by the VRU.

■Whenever dialtone is detected, ensure the VRU digits are outpulsed and the line to DEFINITY is dropped.

The TN744 Call Classifiers required by the Call Prompting feature are not required for returning digits in-band from the VRU to DEFINITY. Instead, general purpose TTR boards (TN748s) are used. As long as dial-ahead digits are available, any collect digits steps following a converse-onstep do not require a TN744 to be allocated to the call.

If no general purpose TTRs are immediately available, and if the call queues for a TTR, no dial tone is provided. For this scenario, the VRU does not outpulse any digits until a TTR is available and dial tone is provided.

If there are no general purpose TTRs available on DEFINITY, and if there is no space in the TTR queue, the operation fails. Usually, the VRU logs an error and then quits, and vector processing continues at the next vector step. Existing system measurements reports inform customers when the system is configured with an insufficient number of TTRs.

H-8Issue 4 September 1995