Freepbx - Asterisk multiline pstn same number setup

I had to setup a multiline on a asterisk PBX the other day for the 1st time, the VoIP was so bad because of the poor broadband, we decided to opt for the multiline pstn option.

I could not really find much on the internet with any help to setup.

So i installed my new fxo card to sit alongside the other that i already had.

The Important settings.

You have to create two Dahdi  trunks - call them say Mulitiline1 and multiline2

My setup in the PBX was actually for 3 pstn dahdi lines incoming and i had 1 fxs card.

Line 1 FXO - Dahdi trunk = channel 1 (original spare bt number)
Line 2 FXO - Dahdi trunk = channel 2 (1st of the multiline channels)
Line 3 FXS - not used at the moment = channel 3
Line 4 FXO -- Dahdi trunk = channel 4 (2nd of the multiline channels)

On my setup it sends to the ivr then queues the calls to the two office phones.

Actually the owner wanted 3 options on the ivr, you may ask how do you know what the call is for if it rings the same two phones at the same time.

What i did was to make an announcement, for example if one is press by the caller for sales, the announcement  tells either phone sales and they then know what the call is for. Two is for enquiries and information etc etc

The first trunk should go through to the ivr, followed by the second which is automatically switched at the phone exchange.

The outgoing rules are very important  to make this work.

In your outbound route
where the section at the bottom for
Trunk sequence for Matched Routes is
add multiline1 then add multiline2 for your failover.

Finally back to the trunks edit your multiline1 and set max calls to 1
this then tells asterisk that the line is busy when in use and it drops through to multiline2.

Of course to keep the the multiline as free as possible, you may want to use another line for outbound calling or VoIP if your broadband is better than ours.