[Asterisk-Users] Analog terminals and modems? does it work

[Rich Adamson]

> I have seen in several places where the analog adapters you can use for faxes and 
modems have intermittent problems. Is this an issue with asterisk and are there 
work-arounds? 
> 
> We currently have side-stepped the issue by sharing the analog line between the tdm 
card and the fax machine (I assume the tdm checks for dial-tone before trying to assign 
the line.)  Long term, I am not so certain this is the idea solution, so I was hoping 
for some experienced feedback.
> 

As has been noted several times, attempts to use modems over voip connections
will be less then reliable, incluidng the tdm card. Part of the reason is
the type of modulation used with some modems and part of it relates to 
tdm issues moving data across the pci bus (and/or interrupt latency).

The slower the modem, the more likely you can get something to work.

The tdm (and associated drivers) do not check for dialtone before dialing.