[Asterisk-Dev] Asterisk voicemail and analog handset on the same line?

[Michael Grabinski]

Hey folks,

I attempted to set up a small asterisk-based phone system for our office
using a couple of X100P to analog lines, and a few Grandstream Budgetone
phones.

I encountered a number of problems.  A bad echo, dropped calls, DTMF working
sporadically.  Searching the list yielded a small improvement in the echo,
but I can't get things working well enough that my co-workers aren't
frustrated on a daily basis with the system.

Anyway, I am abandoning the Budgetone phones for incoming/outgoing calls,
but the asterisk voicemail works great so I want to keep it.

The crux of my problem is this:

I would like to run the asterisk box and two analog phones on the same phone
line.  Collisions only occur with incoming calls because the asterisk box
does not place outgoing calls.

If someone answers an incoming call on a line shared with the asterisk box,
it has no way of "knowing" the call was answered and plays the
auto-attendent greeting after 20 seconds.

Is there a way for asterisk to "know" that a call has been answered by a
phone on the same analog line as the asterisk box, if the answering phone is
not hooked up to the box via a TDM400P for example?  Can it listen for rings
and not answer if the rings are no longer present.

The only thing I was able to think of was having the users key in a sequence
to shut the auto-attendent off when they're in the office and turn it back
on when they leave, but that seems like an error-prone hack to me.

I don't have any knowledge about the switching mechanics that asterisk uses,
so I would appreciate any help in salvaging what's left of the system.
Thanks.