[Asterisk-Users] creating conference call

[Keiron Liddle]

Hi,

I am looking at a project using asterisk for a particular purpose. We 
already are using an Asterisk box for things like voicemail, call 
recording, ip phones etc. and it connects to an old standard PBX through 
ZAP.

What I am looking to do is have calls coming into asterisk via either 
VOIP or ZAP which are then connected through ZAP to the old PBX and out 
into the normal PSTN. That part I can handle, what I need is to be able 
to programatically put the external channel on hold, create a conference 
by dialling into another ZAP channel then after some conversation 
bringing back the one on hold into the conference, the the original call 
from the VOIP/ZAP can be hung up leaving the other two together.

So basically is it possible with Asterisk to:
- identify the channel by outgoing ph no.
- put the channel on hold
- dial through a new channel with conference
- bring back the hold
- drop the original channel and leave the others

 From what I understand of the way asterisk works this should be 
technically possible but I don't know of any way to implement this, 
maybe I need to make some change to the asterisk code?

I cannot do the hold/conference from the phone or originating switch, 
this is a few interfaces down the line, I just want to be able to put 
asterisk in the middle to perform this function most likely through some 
computer program (I guess it would also be possible to detect a DTMF 
sequence to trigger the action).

Does anyone have any ideas about how I could implement this?

Any help is appreciated.

Keiron Liddle