Reference Guide for the Model XM128 ISDN Digital Modem

User-To-User Information

The Model XM128 modem supports user-to-user information exchange via the D channel. To transmit a message, use the ATT4<message.....> command. The angle brackets (< >) are part of

this command. The message is included in a user-to-user information element, which is sent with the first valid message that follows.

If the ATT4<message.....> command is issued before dialing, the user-to-user information element

is sent in the setup message. Whether the information element can be sent to the called party or not is switch dependent. If the switch supports this information element, the called party can see the message before the call is answered.

During a call connection session, the D channel is still used to exchange user-to-user information. For the single stream configuration, both sides must be in Escaped state because only then can they send the AT commands and view the responses.

The user-to-user information element is a supplementary service that has to be invoked on a per-call basis.

Advanced ISDN

7-13

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NETGEAR XM128 ISDN manual User-To-User Information