[Asterisk-Users] Which is the best signalling for FXS

[Rich Adamson]

> > Kewlstart is for disconnect supervision. If you have a simple phone
> > connected, it doesn't make much difference what your signalling is as
> > the human will actually hangup the phone. If you hookup another device
> > that might actually need the supervision like a
> > modem/faxmachine/whatever, you will still want disconnect supervision.
> > As far as technical best, out side of the disconnect supervision, the
> > kewlstart and loopstart are equivalent.
> 
> It is also my understanding that most local exchanges (in the US) don't
> enable disconnect supervision by default. I had to ask my telephone
> company to enable it.

That's not true. In fact, most US telco switches do support disconnect
supervision. Are you sure your not confusing disconnect supervision with
something else, maybe which end of a call 'controls' the disconnect
signalling?

There are likely lots of US systems that are oriented around "calling 
party" control verses "called party" control of disconnect. But once the
central office has decided to disconnect the call (regardless of cause)
you should "see" disconnect supervision in the US in the form of either
a drop of tip-ring voltage (to nothing) for about 400 milliseconds or so,
or polarity reversal for the same approx 400 milliseconds. (Both can
easily been seen with a cheap voltmeter placed across tip/ring.)