Rich Greenberg wrote:
In article ,
Steve wrote:
When you dial a phone number that's long distance but you don't dial
1 first, you get that really obnoxious high-pitched squeal before
getting the recording. It's been that way forever. Why is that
squealing sound necessary?

Probably a large dose of "thats the way we have always done it".

Its actually 3 tones. I don't recall the frequencies or durations,
google could probably find them for you. Its called SIT (Special
Information Tones) and its used by automatic callers to know they have
reached a bad number.

I used that tone (wav.sit) on my answering machine before the do-not-call list
thing to get rid of junk calls. Supposedly, the auto callers remove that number
from their list if they hear it. The junk calls to my phone definately went down
after a few months.