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Non-Standard Facilities Frame

ITU T.30 allows a non-standard message, one not defined in T.30, to be included with most negotiations. These non-standard frames are called NSF when the called fax terminal sends DIS, NSS when the calling fax terminal responds to DIS with DCS, and NSC when commanding the called fax terminal to send (a poll). A non-standard frame begins with the country code of the manufacturer, the manufacturer's code, and any additional ASCII information (limited by allowable transmission time of three seconds). The non-standard frame transmitted by the remote terminal will only be read if the first three bytes match the Country Code and Manufacturer's ID parameters for this terminal.
The version of T.30 approved by the ITU in April 1993 includes new frames to specify an individual fax recipient and document identification for polling. However, until adoption of this new version of T.30 is widespread, manufacturers may use the non-standard frames to specify this information.

Identification During Polling

When an application is using polling, some form of identification or validation may be desired to insure that only authorized parties are receiving faxes as a result of polling. Information about the caller can be placed in the CIG/NSC fields by the calling application (the poller), and verified by the called application. The CIG field contains the telephone number of the polling terminal. The NSC field begins with the country code of the manufacturer (USA), followed by the two-byte manufacturer's code. The remainder of the NSC contains manufacturer-specific information. This may include a password as well as an identification of the desired document or fax mailbox.

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