I've noticed recently that when I call france from Ireland on an eircom line that the french ringing tone doesn't appear.. i immediately get an irish ringing tone! completely replacing the french one.
Same with calls to some US numbers.
Is this meant to happen or is it a glitch in the signaling? Seems like when the French / US system sends a signal saying it's ringing our local exchange provides its normal ringing tone.
I've not noticed that on any international calls from the U.K.
The common-channel digital signaling on overseas circuits means that tricks like this can be done though. Starting a few years ago, some carriers have been applying busy tone on the originating end. In the past, if you called a number which was busy in the U.S. you would always get an American busy signal from the office you were calling. Now, the distant end can just return a "line busy" code over the common-channel signaling and the originating equipment at this end applies British busy tone. It only seems to be some carriers doing it though.
Some carriers are also using the similar signaling techniques on calls to invalid numbers. You could call the same American number several times in a row and sometimes get an American intercept ("Your call cannot be completed as dialed...") and sometimes get dumped straight to a British "The number you have dialed has not been recognized."
As for your case of applying ringback locally, it would be interesting to see the protocols being used. Keeping the trunk muted and local Irish ringback applied until the trunk signals answer supervision wouldn't be too difficult, but it would prevent you from hearing any intercept recordings from the U.S. end (because they don't return supervision). I sure hope they thought of that and allowed for it! There'd have to be more detailed signaling passed over the CC circuit than just answer supervision.
Actually makes a lot of sense from an end user perspective!
I'm not so sure. For someone making his first faltering attempt at an overseas call I suppose it might be comforting to hear a familiar ringback tone. But for anyone else who is
expecting to hear a French or American ring, I'd say it's somewhat confusing. They'll probably think they misdialed and are accidentally ringing a phone within Ireland.
In the case of the locally applied busy signal, I don't like it, but the TelCos would probably argue that the trunk can be freed that much more quickly for the next call. In the case of a ringback signal, any such argument doesn't apply because the trunk has to be held until the call either answers or times-out anyway.
[This message has been edited by pauluk (edited 02-11-2003).]
