We are using hylafax with a VOIP PBX which results in poor
quality phone lines and lots of hdlc fcs errors. We would like to try reducing
the fax datarate to see if this helps reduce errors. Our modem supports V.17,
V.29, V.27ter and V.21 channel 2. I notice that Hylafax always issues a +FRH=3
command to my modem. Apparently the +FRH command sets the protocol and rate.
Maybe this could be used, but hylafax doesn’t seem to support changing
the value provided in the +FRH command.
+FRH=n causes SoftModem to receive frames using HDLC
protocol and the modulation defined below. An ERROR response code results if
this command is issued while SoftModem is on-hook.
+FRH=3 V.21 channel 2 300 bps
+FRH=24 V.27 ter 2400 bps
+FRH=48 V.27 ter 4800 bps
+FRH=72 V.29 7200 bps
+FRH=96 V.29 9600 bps
+FRH=73 V.17 7200 bps (long train)
+FRH=74 V.17 7200 bps (short train)
+FRH=97 V.17 9600 bps (long train)
+FRH=98 V.17 9600 bps (long train)
+FRH=121 V.17 12000 bps (long train)
+FRH=122 V.17 12000 bps (short train)
+FRH=145 V.17 14400 bps (long train)
+FRH=146 V.17 14400 bps (short train)
From my hylafax session logs I see that the sending FAX
modem is suggesting that we use v.17 14400bps
Apr 07 11:28:32.07: [18832]: REMOTE wants 14400 bit/s
Apr 07 11:28:32.07: [18832]: REMOTE wants A4 page width
(215 mm)
Apr 07 11:28:32.07: [18832]: REMOTE wants unlimited page
length
Apr 07 11:28:32.07: [18832]: REMOTE wants 3.85 line/mm
Apr 07 11:28:32.07: [18832]: REMOTE wants 2-D MMR
Apr 07 11:28:32.07: [18832]: REMOTE wants T.30 Annex A,
256-byte ECM
Apr 07 11:28:32.07: [18832]: RECV training at v.17 14400
bit/s
Does the receiving FAX machine have any way to negotiate
say V.29 9600bps instead?
John Matthews
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