Table 24. Fax phase sequence Sequence Calling station Called station 1 Ring signal Phase A—Call setup sequence 2 CNG tone beep, 1100Hz 1 second 3 Transmit CED, 3 seconds, 2100 Hz 4 Transmit NSF 5 Transmit CSI 6 Transmit DIS 7 DIS detected Phase B—Pre-message procedure (negotiate compatible format/protocol) 8 Transmit TSI 9 Transmit DCS, select mode 10 DCS detected 11 Transmit TCF/training 12 Transmit FSK 13 Training (synchronize signals), check for errors 14 Transmit CFR 15 Detect CFR 16 Transmit message (FSK, followed by date) Phase C—Message transmission (page/scan transmission) 17 Receive message (SCAN), check for errors 18 Transmit FSK 19 At end of message, send one of the following:
EOM EOP MPS PRI-Q PPS-NULL PPS-MPS PPS-EOM PPS-EOP PPS-PRI-Q Phase D—Post-message transmission (next page/end of transmission) 20 Detect EOM, EOP, MPS, PRI-Q, PPS-NULL, PPS-MPS, PPS-EOM, PPS-EOP, or PPS-PRI-Q 21 Transmit MCF response to confirmation signals of post-message responses Phase E—Call release (hangup sequence) 21 Transmit DCN 22 Station hangs up EN Troubleshooting tools 223