I've noticed this caller-hears-ring-before-actual-ring thing, too (also on AT&T). I always presumed it was a way of giving them (the network) a little longer to make the actual connection, without the caller giving up thinking "it hasn't even begun to ring yet! Something's wrong!"

That's what this seems to be, I've even noticed that the first ring may even sound a bit different from subsequent rings.

I think the first layer ring is the actual call setup being attempted across the cellular network. Once the receiving phone is located and receives the signal that a call is incoming, you begin to hear the second layer ring.

The ring that the caller hears is basically just a recording. And yes, that's it's purpose.. so you know it's doing something before it's actually completed.

It's the telecom equivalent of the loading pinwheel.

The term you're looking for is 'ring-back', and it's original use seems to have gone the way of the do-do in North America.

Most of the PBX/VoIP systems I've worked on (North and South America) provide one arbitrarily to give the caller the warm and fuzzies, regardless of what's actually happening to that call leg.

And as a mobile subscriber you can usually pay for a custom "ring-back" tone. So you can bother anyone who calls you with the latest Rihanna hit.

What if the callee has their phone on silent?

j/k

The "ringer" tone is to let you know the call is going through, and in the case of you calling a cell phone, that the network is trying to connect to your callee.

A cell phone gets a signal to play it's ringtone, not a "ring now"..."ring now"... on / off signal. Did you expect to hear my ringtone on your end?

I said 'ringer-tone' and not ringtone. Please read comments or posts carefully before commenting replies and 'j/k's.

I also recommend that you read the community guidelines here -- http://ycombinator.com/newsguidelines.html

It's just the auditory equivalent of a wait cursor.

It has to do with the codes of signalling in the various protocols such as SS7, h323 and SIP. Taking SIP as an example code 180 is call progress connecting and a signal is generated that sounds like ringing while code 183 allows you to actually hear the sound being generated on the other end, which is how they create the custom ring tones or when you will hear the international ring tone. While 183 is the actual signal the 180 code is far more efficient and is what is used by the larger carriers.

It may just be a signal to the caller that something is happening. Otherwise you're left wondering with whether the call went through or not.

Even on land line phones, the ring indication tone is not evidence that the remote phone is actually ringing. If I remember correctly, the tone is generated by the equipment at your central office, not at the remote location.

Original idea is that ring tone is generated by same exchange that provides the ringing voltage to analog local loop that rings. Idea there is that it tests that the whole connection is built correctly and can pass this ring tone. On the other hand this is horribly inefficient and thus often ring tone is generated on another places. For this cell phon behavior it's entirely imaginable that (G)MSC (lets just use GSM terminology) starts generating ring tone when it had found correct MS in location registry and sent paging request to it, obviously there can be significant latency between that and actual user observable ring on the terminating MS (on the order of 200ms in best case, few seconds or call being dropped in worst).

Even if I make a call from Skype to my cell phone, I can hear the audible "ring" on Skype long before my actual phone begins to ring.

Dial tones were always meant to be just a signal that the Caller has reached the Switch and there is an attempt to make the call happen. It was never meant to synchronize with the actual Called party's phone. Fixed line phones simply get an electrical signal to make the phone "ring"