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

[james]

> > 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.)

That's what I was looking for and the telco wasn't providing it. I found
this in both Pennsylvania and New Hampshire. Both were little mom & pop
phone companies. They said that DS can cause a click in the reciever of
some phones so they normally turned it off.