[josh2600]

Technically speaking, it's only on SS7 networks where this is a problem to implement. It's basically just playing an arbitrary media file, which is trivial in VoIP.

The interesting thing is that the original SS7 code did not have an arbitrary case programmed for the ring back tone; that is to say the original network infrastructure did not support on-demand changes to ring backs or to pull an arbitrary media file at the time of call. The solution was a box intermediating the call to stream musical media before connecting to the actual intended voice call media.

Telecom, why do stuff in softwhere when you can just add another box?

[MBCook]

If I were designing that system that's what I would have done.

I can't think of an actual need for that ability, only the fact it could be used for novelty, abused to annoy people, or just flat out cause problems (i.e. what if my ringback tone is a busy signal?)

[pmorici]

It's used as a cheap way to implement a school closing hotline where people all call to receive the same message.

[MBCook]

You came up with something, I'm impressed. I don't think that would be the best way to implement that but it's a sane idea and one more than I had.

Edit: after reading more in the thread, I see you actually ENCOUNTERED this. Why do it this way? Would it somehow be cheaper because you don't have to 'answer' the calls and hold the lines open?

[startledmarmot]

It really boils down to money. When the call connects, somebody gets charged. Perhaps both of you do -- you lose a minute on your cellphone bill, and the school gets charged a minute for the phone call.

Putting the school notice in the RBT space eliminates this charge and essentially makes the entire transaction "free."

Lots of big companies use this for the first step in their automated attendants. Since DTMF (phone number signals) are transmitted during the ringback tone (but voice is not), they can put the first step of their attendant in the RBT space. This saves them the money if you never get any further, or decide to hang up soon after.

[josh2600]

The settlement agreements for calls are pretty straightforward (Sending party pays). Consumers are also billed for service, but behind the scenes there's a wholesale market where traffic imbalances are valuable (this is also a core issue with Net Neutrality; consider that at peak Netflix is 35% of global bandwidth which is mostly delivered by one provider: cogent).

There's a whole different discussion around signaling and abusing both headers and early media transfers to avoid billing. It's still very largely the wild west, IMHO.

[startledmarmot]

Truthfully, regarding call connect charges, ringback, per-minute fees, etc... I don't think many folks think much about the fact that a lot of the business and billing decisions driving modern telecom policy are still rooted in the same thought patterns they were in the 1950s. It drives the net neutrality debates, it drives shareholder profit expectations, everything.

And I agree - it's absolutely the wild west. After 70 years of doing it one way, we're starting to see a tipping point of new realtime infrastructures and technologies. Unfortunately, I think it's likely to become even more wild as the "silo-ification of communication" trend continues. Boo.

Don't get me started on credit card processing fees. ;)

[kijin]

> (i.e. what if my ringback tone is a busy signal?)

My father used to take the handset off the hook during important family meetings. Anyone who called during that time got a busy signal. This was long before ringback tones were a thing.

I've also heard of a similar technique being used to fight telemarketers a few years ago. Many telemarketers run a program that automatically detects nonexistent numbers and removes them from the list. So this guy made an app to imitate the phone company's 404 error msg (or whatever the audio equivalent is) whenever he received a call from a known telemarketer. I don't know whether he did it with a ringback tone or just played an mp3 after picking up, but anyway, he no longer received any calls from telemarketers after a while.

[krupan]

You make me feel old. Yes, it was in the late '90s and early 2000's that you could buy the Telezapper. It was a little box that connected between the wall jack and your phone and played the little three-tone "number disconnected" sound whenever you picked up your phone. The telemarketer's computer would then (so they said) register your number as disconnected and they would never call you back. If a human called they would hear the tone too and sometimes hang up right away thinking they had mis-dialed. Small price to pay to get rid of telemarketer calls, though :-)

[kijin]

Found it! http://www.k3pgp.org/telezap.htm

Another trick was to play the fax tone. But as the link above says, you risked getting spam faxes if you played the fax tone.