Phones independent to Asterisk

Hi all,

I did a search on this, but couldn’t really find an answer.

I have a Cisco 7940 that I would like to use in combination with Asterisk to make both VoIP calls and calls via my PSTN line (through an FXO card that I would have to buy). However, it is practically impossible to connect all of my analog phones in the house to the Asterisk server.

So my question is this, if someone calls me via the pstn line, will the presence of Asterisk affect the other phones (will they not ring or only very shortly?) or will both the independent analog phones and the SIP phones connected to Asterisk ring until one of them picks up?

Thanks in advance,


It depends on how you setup the FXO card.

In one mode (immediate answer) the Asterisk box would answer the call right away and continue to provide ringing to the caller in the form of a tone played to the analog line port. However, the call is actually answered by the Asterisk box, so the other analog lines would no longer be ringing.

If you do not use immediate answer mode, the analog lines in your house will ring normally. However, your 7940 will not start to ring until the CallerId information has been received. This means your analog lines in your house will ring twice, (CallerID information is sent between the first and second ring in North America) and then the Asterisk box will start the call to the 7940.

OK, so with the second option, when I get a call, all the analog phones will start ringing and after the second ring, the Cisco 7940 will also start ringing, together with the analogs?

That works for me. Thanks for your help!


That’s right.

It’ll behave just like your other phone devices.

Don’t forget things like your answering machine or phone company voicemail. They may answer calls before you get a chance to pick up the call on the 7940.

The timing of rings may become important if you intend to use both an answering machine and the Asterisk Voicemail.