asterisk users - Mar 2005 - call pick up and joining an active call

I am looking at buying either a TDM411B or TDM431B to play around with
Asterisk at home.

What I am wondering is if I could use the TDM431B to divide our phone lines
into 3 groups to use as an intercom, but still have them work normally
for answering calls and calling outside.

I found commands for checking if a channel is in use, so I should be able to
do different things depending on whether or not there is a call using the
outside line or if some other phones were picked up.

It looks like there is a way to do complicated things when a phone is
picked up, so I think I can have it get a dial tone if no other phones
are in use and there isn't an inbound call. Answering a call from outside
or inside, can probably be handled by pickup groups. I wasn't sure if
there was a good way to join an existing call. I read through the MeetAt
documentation I could find and it looks like it may be able to set
up a conference for every call, but I am not completely sure if this
was really possible or if this would be the best way to do things.

Being able to do this would make paying the extra for the TDM431B worthwhile.
(I don't have broadband, so have multiple local phone channels won't let
me make multiple simultaneous calls.) Otherwise I will probably get the
TDM411B and leave the 2 slots for future expansion.

I really don't need a detailed how to do this right now, but just whether
or not it is doable.

Thanks for your help.

On Wed, Mar 23, 2005 at 13:00:57 -0600,
  Bruno Wolff III <bruno@wolff.to> wrote:
> 
> What I am wondering is if I could use the TDM431B to divide our phone lines
> into 3 groups to use as an intercom, but still have them work normally
> for answering calls and calling outside.
It looks like I do need a conference to mix 3 channels together.
There is a way to redirect a normal 2 party call to a conference.
So I think it will be possible to move an existing call over to a conference
using agi and a program that does the redirect. So that if a second person
picks up a phone after a call has already been answered, it should be possible
to make things look like their phone was connected directly to the phone
of the other person who already picked up.

There are a lot of details for me to work out later, but it looks like this
will be doable.