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Caveat floppy disk Users

A considerable amount of testing has gone into various methods of receiving fax directly to disk (or via memory buffers) using floppy disks. While this is possible for a single page fax, the overhead of SMS/QDOS floppy disk I/O has resulted in the fax protocol timing out on multi-page faxes for every method that has been investigated.

The most likely outcome of direct reception to disk is that you will receive all the first page (but slowly, at the sender's expense), but the overhead of closing the file (flushing slave blocks) will mean that the modem's end of page or end of document handshake will timeout. A transmission error will be generated on the sender's machine, and they may decide to retransmit the fax, which is not only unnecessary, but if it is a long distance or international call, expensive for the sender, and if it happens too often, they may decide not to fax you again. This condition is identifiable by

multiple resends of faxes
the +FHNG:100 reply in a session log.

The normal +FHNG parameter is 0. (+FHNG:0), any non-zero value indicates an error as described in the EIA Class 2 specification.

Reception to disk is a desirable feature, as it provides data security in the event of system or power failure. QFAX implements this using an optional automated backup system whereby faxes are initially received to a ram_ device, and once the end of document handshake has completed, the fax is copied to a disk. This mode of operation is invoked using the VIA parameter to describe an intermediate reception path in your `qfax_dat' file. qfax does not release the phone line (although the caller will have hung up), until the copy has completed.

You should use the VIA parameter if you are receiving to floppy disk or to a slow hard disk on a slow CPU (e.g. Miracle Hard Disk on 68008 CPU). See section VIA keyword.

Reception directly to hard disk should be entirely satisfactory using a fast disk on a ST emulator, SMS system, or QXL .

A typical A4 fax page will occupy between 30-60K bytes. A Trump Card with 600 Kb free will allow you to receive a ten page fax using the VIA parameter, while on a Gold Card with 1 Mb free, you could receive a 17 page fax without error. Once the fax has been received, the memory is freed as the data is copied to disk. Note that a blank 720 Kb disk can only hold 12 A4 pages (at 60 KB/page). If you expect to receive fax at significantly higher volume than this I would recommend that you invest in either a standalone fax machine or a fast CPU and large hard disk system.

If your fax modem supports the Class 2 AT+FPCTO parameter, setting AT+FPTO = 255 in the modem `init' string may allow reception to floppy disk.

Sending of fax may also be effected by floppy disk I/O. If you are sending a document and qfax is reporting reception of unexpected characters, then this is symptomatic of such problems. The sequence of received characters (during send) :

[2b] received while sending data           (+)
[46] received while sending data           (F)
[48] received while sending data           (H)
[4e] received while sending data           (N)
[47] received while sending data           (G)
[3a] received while sending data           (:)
[20] received while sending data           ( )
[34] received while sending data           (4)
[33] received while sending data           (3)

is an error report from the modem +FHNG: 43.

So, if you receive the [2b 46 48 4e 47 3a] sequence while sending, you probably have a data flow problem due to floppy disk delays.

This is a fundamental feature of the way SMS/QDOS I/O works; when the operating system is servicing the floppy disk it cannot also service the serial ports. For reliable fax operation, particularly at v.17/14400 bps) you must use a fast device (or Atari or QXL hardware) .

For some users this means using a `ram_' disk and VIA ram.


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