Re: [hylafax-users] AT+FRM=146 sometimes with timeout

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Matthias Reich wrote:

> Hi List,
>
> sometimes my modem (devolo mircolink II) seems to not respond while receiving 
> a fax. Having a look at the logs, I nearly always see the problem occurs
> when the modem gets the "AT+FRM=146". Reading the archives I found out, the 
> only answers to that command are "OK" or "ERROR". But my modem does not 
> answer at all. As this happens only on one out of hundred faxes, I think it 
> could be that the modem sometimes is not quick enough to answer the command 
> within 7 seconds. 
>
> Is there a parameter that can be changed in the way that hylafax waits for 
> e.g. 10 or 15 seconds from an answer from the modem ?
>
> Mar 01 11:22:01.69: [ 3886]: MODEM input buffering enabled
> Mar 01 11:22:01.69: [ 3886]: <-- [11:AT+FRM=146\r]
> Mar 01 11:22:08.69: [ 3886]: MODEM TIMEOUT: reading line from modem
> Mar 01 11:22:08.89: [ 3886]: MODEM TIMEOUT: reading line from modem
> Mar 01 11:22:08.89: [ 3886]: MODEM <Timeout>
> Mar 01 11:22:08.89: [ 3886]: MODEM input buffering disabled

The AT+FRM=146 command tells the modem to listen for the V.17 14400 bps 
carrier and to report CONNECT when it is found and to then begin passing 
data communicated on that carrier to the DTE (HylaFAX) and then to wait 
for a carrier drop and to then report DLE+ETX bytes and the NO CARRIER 
response.

After waiting 7 seconds for the carrier you can pretty much rest-assured 
that the sender is not going to be sending V.17 14400 without further 
interaction with the receiver.  In fax protocol (non-V.34 protocol) 
everything falls back onto the V.21 messaging carrier... so if things 
don't work out with the high-speed carrier the idea is to fall back and 
listen on V.21 until you get a message, maybe send a message, or you 
give up.

So that's what HylaFAX is trying to do there... it's trying to abort the 
AT+FRM=146 command after 7 seconds but it doesn't go very smoothly.  If 
it is never able to abort smoothly, if the abort attempt always looks 
like this (with multiple "MODEM TIMEOUT: reading line from modem" 
messages), then the modem probably does not support the abort attempt 
that HylaFAX uses (sending CAN character to the modem)... and in that 
case you should use:

 *Class1RecvAbortOK*: 0

In your modem config file.

Now the 7-second timeout can, in reality, be extended with FaxT2Timer.  
But you don't want to do that, believe me.

Lee.


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