[Asterisk-Users] T1 to T1 on asterisk?

[Mark Spencer]

> Nothing like being on the cutting edge. :-)

Always

> What sort of change was required to make this work?

Some changes to chan_zap in how call features are handled.  The zaptel
changes were already there for a while.

> In theory, the modems send the "don't echo cancel" tone to turn
> off echo cancellation in the connection, but I think you are
> suggesting that echo cancellation be manually hard coded off for
> that extension, right?  In that case, is the incoming T1 digital
> stream identical to that handed to the outgoing T1?  Should just
> be a copy inside *, right?

Inside the kernel, actually.  We do look for the echo cancel disable tone,
but to be pedantic might be a good idea, and echo cancellatoin just costs
CPU anyway.

> If that is true, then the bits are not mangled by * at all,
> answering the previous question.  But ISDN is actually *easier*
> in some ways, no DSP on the samples to recover the modulation.

The trouble with ISDN is specifically that there is no "echo cancel
disable" tone preceeding the call.

Mark