Answer
Handshaking failures are commonly encountered during the pre-message procedure. The pre-message procedure (also known as phase B) is the stage where sender and recipient fax device identify, negotiate and select compatible facilities for both fax devices (such as agreeing about a reliable fax transmission speed).
Any handshake failure 54 during phase B will automatically result in a call termination. Common reasons for a handshake failure 54 are:
Any handshake failure 54 during phase B will automatically result in a call termination. Common reasons for a handshake failure 54 are:
- Hangup Status Codes 20: Unspecified Transmit Phase B error
- Hangup Status Codes 21:Remote cannot receive or send
- Hangup Status Codes 22:COMREC error in transmit Phase B
- Hangup Status Codes 23:COMREC invalid command received
- Hangup Status Codes 24:RSPEC error
- Hangup Status Codes 25:DCS sent three times without response
- Hangup Status Codes 26:DIS/DTC received 3 times; DCS not recognized
- Hangup Status Codes 27:Failure to train at 2400 bps or + FMINSP value
- Hangup Status Codes 28:RSPREC invalid response received
Some of the hangup status codes are related to poor quality phone lines which may cause handshaking errors.
Things that can cause quality issues with phone lines are:
- Sharing of fax lines with voice equipment or other fax machines
- Electro-magnetic interference on the lines themselves or introduced via couplers/splitters
- Faxing over a voice-over-IP line
- DSL lines (in particular, DSL with no filters in use)
- Poor-quality cabling and/or loose connections, etc.
If the issue occurs with a particular sender or recipient, it is most likely an issue with the telephony configuration at the remote party's end, however checking all of the above within the local telephony configuration is a good start.