I am having intermittent problems with my FXO/FXS ports. Basically I have fax machines attached. Every so often (sometimes 5-10 days in between), the fax machine says that it has no dial tone. I am able to resolve the problem by going to the CLI and unloading mod_freetdm and then reloading mod_freetdm. When the “no dialtone problem” is happening, unloading mod_freetdm takes 10 seconds or so…I have even had it crash freeswitch during the unload…
Whenever this problem happens, you need to enable debug logging in FreeSWITCH. Dialtone is provided by freetdm not the card, but if the card does not detect the fax going offhook, then no dialtone will be provided. First thing is to determine whether FreeTDM receives the offhook event from the card/drivers, that can be seen if debug logging is enabled (some message saying something like "wanpipe event x received").