An AWESOME feature request....

[rx100]

Voicepulse's "Telemarketer Block" feature is also very effective. The caller will hear a short tone (just like the one for a disconnected phone number) before your phone starts ringing and that triggers removal of your number(robodialer) from the telemarketer list.

[usa2k]

If cell companies can play songs to the caller, instead of ringing, does that mean they connected the call? If you get a lot of LD inbound, are you guaranteeing the caller has termination fees? I guess they must. That is revenue for the cell company each time.

VOIPo could be accused of trying to get additional revenue by the extra call handling. Voicemail likely has the same termination costs to the caller's service.

I expect this involves a different method of internal call routing, and is not just a hand-off to a switch. (Wish I were more technically savvy about this.)

[VOIPoDanielC]

If cell companies can play songs to the caller, instead of ringing, does that mean they connected the call? If you get a lot of LD inbound, are you guaranteeing the caller has termination fees? I guess they must. That is revenue for the cell company each time.

Not really... Audio can be sent before a call is connected to replace the standard ringing sound. Once the call is connected, the "ringing" stops. This is called "early media".

You can tell which cell phone providers are using SIP in their backbone this way...

Here's the RFC, if you'd like to take a look: http://www.ietf.org/rfc/rfc3960.txt