I run a law office and we have to have a fax capability that I would prefer to maintain locally.
Faxing has become problematic in the last few days and I don’t know why. Some faxes make it, some don’t. Our FIOS provider was bought out by T-Mobile recently, but we haven’t noticed any difference in internet service.
It was suggested to slow the baud rate to 2400 (from 14400) and I tried to do that by editing the res_fax_custom.conf to add “minrate=2400” and “maxrate=2400” and doing a “core reload” on the CLI, but “fax show settings” shows that the change isn’t working - the minrate remains 9600 and maxrate is 14400
You will save yourself a lot of pain by getting POTS line from your LEC and plugging it into a decent printer/copier/fax multifunction device (like something from Ricoh) and then loading the desktop software faxing on your PC’s that connects to the printer so your users can fax from the desktop via the printer, instead of kluging it through the PBX. You probably even already have such a piece of equipment around in service.
FAX is such dinosaur technology these days that doing it as old-school as possible is the only way it will work anymore.
I doubt that even if you have a knob to select 2400 bps that your fax hardware will drop to this antique Group 1 speed. Most likely the lowest the hardware will allow is 4800 which should force Group 2. Anything higher and the board will connect at Group 3.
But if you must persist, then go find a garbage dump or Dumpster or visit an e-waste recycling center and with luck you may find some 1991 antique piece of garbage thermal paper fax machine. This then becomes your test machine. Find a recipient that your unable to fax to from the PBX and temporarily unplug the PBX and plug in this machine then try sending a fax from it. If that also fails then it’s your POTS line.