Xerox Phaser 6128MFP Service Manual page 116

Theory of Operation
2-62
The sending side sends out a Calling Tone (CNG.1100Hz for 0.5 sec.), which
identifies itself as a fax terminal. Then, the receiving side responds with a
Called Station Identification (CED.2100Hz for 3 sec.) to identify itself as an
available fax terminal. Thus, a fax call is established between the two
terminals.
• Phase B – Capability Negotiations
The receiving side presents all of the capabilities it has to offer by sending out
NSF/CSI/DIS signals. Then, the sending side responds with NSS/TSI/DCS
signals to declare what it has selected from the capabilities presented by the
receiving side.
The sending side sends out a training signal (TCF) to adjust the modem to the
maximum transmission rate available. Upon a successful reception of TCF, the
receiving side responds with Confirmation to Receive (CFR), which indicates
that the receiving side is ready for receiving image data. In the event of an
abnormal TCF reception, the receiving side responds with Failure to Train
(FTT), which requests retransmission of NSS/TSI/DCS and TCF signals.
• Phase C – Image Data Transfer
The sending side transmits the image data based on the parameters agreed
upon in Phase B. Also carried out are the signaling control procedures
including synchronization, error detection/correction, and line supervision.
• Phase D – Post-transfer Procedure
In the Post-transfer Procedure, the sending side checks its status after the
completion of Phase C and sends an appropriate signal to return the session
to the previous phases. When there are more pages to follow, the sending side
sends out Multi-Page Signal (MPS) and the session returns to Phase C. When
there are more pages to follow and the subsequent page is to be sent in a
different mode, the sending side sends out End of Message (EOM) and the
session returns to Phase B. The session proceeds to Phase E only when the
receiving side receives End of Procedure (EOP) indicating that the sending side
has completed transmission of the entire document. Therefore, the session
may show a looped sequence such as ABCDCD...E, ABCDBCDBCD...E. etc.,
depending on the remainder of the document or the transmission parameters
for the subsequent page.
Phaser 6128MFP Service Manual