PMDF System Manager's Guide

The G3_TO_FAX channel is the channel which actually delivers a PMDF-FAX message. This channel communicates directly with the FAX modem to initiate each call and transmit each FAX message. Each "G3" file stored in the G3_TO_FAX channel queue directory represents a single message and may have up to 65,535 different recipients, each with different FAX telephone numbers. In the preamble section of the G3 file, the following information is stored for each recipient of the message: the number of delivery attempts (0--253), and the delivery status (delivered successfully; retransmit; permanent delivery error). The "retransmit" delivery status is equivalent to a "temporary delivery error". Each time the G3_TO_FAX channel processes a G3 file, delivery attempts are tried for each recipient marked retransmit. Up to 253 delivery attempts will be made for each recipient who is marked retransmit; if the message cannot be delivered to that recipient after 253 attempts, the recipient is marked "permanent delivery error" and an e-mail message is sent back to the message's originator. The G3 file will be removed from the queue only when no recipients are marked for retransmission. (Note: The maximum number of allowable delivery attempts may be controlled with the MAX_DELIVERY_ATTEMPTS option for the G3_TO_FAX channel.)

When an error occurs while placing a call, one of several actions is taken:

1. No answer after 10 rings: If there are no alternate FAX telephone numbers to attempt,⁴ the recipient is marked retransmit, the current system time is recorded, and the FAX message is requeued for later transmission.
2. Busy signal: If there are no alternate FAX telephone numbers to attempt, the recipient is marked retransmit, the current system time is recorded, and the FAX message is requeued for later transmission. The possibility exists that a busy signal may be mistaken for a human voice. Most FAX modems, however, tend to make the opposite mistake more often: the FAX modem errs on the side of taking voice responses to be busy signals rather than calling busy signals voice responses.
3. Dead line: If there are no alternate FAX telephone numbers to attempt, the recipient is marked retransmit, the current time is recorded, and the FAX message is requeued for later transmission.
4. Human voice or other non Group 3 compatible device: If there are no alternate FAX telephone numbers to attempt, this is treated as a fatal delivery error and an error message is sent via e-mail to the message originator. The recipient is marked "permanent delivery error" and the current time noted. The message will remain in the queue if delivery to other recipients is still required.
5. Broken connection: If there are no alternate FAX telephone numbers to attempt, the recipient is marked retransmit and the FAX message is requeued for later transmission.

The FAX modem may report transmission errors for individual FAX pages. When this occurs, no attempt is made to retransmit the pages in error. A notification is, however, sent to the message originator listing the page numbers on which transmission errors occurred. (In such reports, the cover page is counted as the first page.) These reported errors owe themselves to line noise and usually affect only one or two scanlines on the transmitted page. When line noise is severe, one of the two FAX devices typically aborts the connection thereby causing the message to be requeued for later transmission.