On Tue 11 Mar at 01:00 Ian Smith (3:626/660{at}fidonet) wrote to Arthur Marsh:

 RS> Bet you would with V.29

 IS> ?  V.29 is a leased-line protocol.

 AM> Well, a half-duplex protocol that was used by the then
 AM> Telstra for "fast training" modems,

 IS> On switched lines?

Not sure.

 AM> and is still used by facsimile machines.

 IS> I wonder how?  Ok, I initially relied on my usually reliable 
 IS> Dataplex product catalogue's Technical Reference section, 
 IS> defining V.29 as a "9600bps modem standardised for use on 
 IS> point-to-point 4-wire leased telephone-type circuits."

 AM> Uyless Black or Frank Nitzsche could probably add more 
 AM> detail (-:.

 IS> Uyless Black, in the OSI book, from the table of V-Series 
 IS> Interfaces, p.69:

 IS> Series Number:        V.29    V.29    V.29
 IS> Channel Line Speed:   9600    7200    4800
 IS> Separation:           4-wire   ''      ''    <<<
 IS> Modulation Rate:      2400     ''      ''
 IS> Carrier Frequency:    1700     ''      ''
 IS> Use of V.2:           Yes      ''      ''
 IS> FDX or HDX:           Either   ''      ''    <<<
 IS> Sync or Async:        Synchronous      ''
 IS> Modulation Technique: QAM     PS      PS
 IS> Bits Encoded:         4:1     3:1     2:1
 IS> Backward Channel:     Not Defined
 IS> Switched Lines:       No      No      No     <<<
 IS> Leased Lines:         PP 4W   PP 4W   PP 4W  <<<
 IS> Use of V.25           Not Defined
 IS> Use of V.28:          Yes      ''      ''
 IS> ISO Pin Connector:    2110     ''      ''
 IS> Equalisation:         Adaptive ''      ''
 IS> Scrambler:            Yes      ''      ''

 IS> As of 1991, anyway .. was there a revision for switched line 
 IS> (or 2-wire) use?

Group 3 Facsimile uses V.29 in switched, two wire, half duplex mode, and
includes option for error correction mode (ECM) which is required for the
binary file transfer (BFT) option.

Not exactly a "V-Series modem", but is does provide the
capabilities to send and receive files over 2 wire voice band lines with
help from V.21 between pages/files.

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