Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

FXO Connections


I´ve had some problems regarding using FXO lines from reouter to PBX. Descibsion below:

1. I call The Router

2. Get another dialtone

3. Chose a number to any extension connected on the Routernet.

4. Don´t get any answer and hang up.

Problem is that after I hang up the extension I dialled will still be ringing. And on some occations the Co Line for the PBX will "freeze".

Is there any Disconnect clear signal on the router that can fix this?

Think there is a simular problem if you connect a internal number from the PBX to the router and then on the other side put up an FXS port. Then if you call the internal number (or through DDI) the phone on the other site will ring ...if you hang up the phone will ring for some time.

Any fix ?

Thanks :)

Cisco Employee

Re: FXO Connections

The PBX needs to send a disconnect signal to the FXO port on the router in order for the router to go back on-hook again. The standard way to do this is a denial of battery power -- I believe the specification says to do this for 350ms or more. This is what most PSTN switches will do to a home phone line if the far end sends a disconnect signal.

Or, if you have the FXO-M1 card on the router, then the PBX could also do a battery reversal (tip-ring reversal) to indicate that the call is disconnected and we should go back on-hook.

Either one of those methods should work.

New Member

Re: FXO Connections


Have checked the PBX and there is no such signalling on the analoge ports of the PBX , that I can adjust. I´ve tried other PBX´s also (LG,Alcatel,Phillips,Ascom and Hybrex) without finding any Disconnect Signalling on the Analoge port (Single Line). So ... my problem is still there :)

I found another Disconnect signal...but that has to do with the Trunk Lines og the PBX not the Analoge phones.