[asterisk-users] using asterisk on a shared line

[Dana Harding]

> The box running Asterisk isn't on 24/7 so I have a secondary phone
> connected to the line as well. If Asterisk is not running, I can
> answer an incoming call from that phone. If asterisk is running, I can
> answer the call from a sip extension.
>
> Can I have it both ways? Can Asterisk back off if the secondary phone
> answers the call? Currently, if a call comes in and I answer it from
> the secondary phone Asterisk will continue to ring the sip extension
> and eventually drop into voicemail.

You don't say how your Asterisk is currently connected to the PSTN line.

Running Asterisk 24/7 would probably be the simplest.
If adding some hardware is an option, it can be done by using an ATA for 
your secondary phone.

Use an ATA that has both an FXO and FXS port, and bridges the two when power 
is lost. (such as the SPA-3102)
You can either do some fancy wiring to power off the ATA when the asterisk 
box is shut down,  or simply use a power bar. (shut down the asterisk box 
properly before killing it's power....)

Normal operation:   PSTN line rings,   Asterisk sees this and calls the sip 
extensions,  including the sip extension of your secondary phone (via the 
ATA).    The ATA will also see the line ringing on it's FXO port,  but is 
configured to do nothing.

Asterisk-off operation:  PSTN line rings,  asterisk is off so it does 
nothing, ATA is also off and has automatically bridged PSTN to the secondary 
phone.

This approach also ensures that the secondary phone can still be used in 
emergencies if the Asterisk box has crashed,  or during a power outage (* 
provided that the secondary phone does not, itself, require power to 
operate).