High screech sound over telephone?

[Guest nanop]

Hi, hust want ur feedback and what u think about this:

I have a telephone that when u put ur hands over the mic in a special position, it makes a high screeh sound. I sometimes use this if I get a call from telephone "advertisers". They r really annoying, sometimes, the call doesn't get hanged up (disconnected) when I hang up the phone and make another call. The question is, would they hear this on their speaker ( or there phone filters/blocks the sound? Is this also legal?

(Don't tell me about the DO-NOT-CALL thing)

-Thanks 4 ur Help

[audioguru]

The sound is caused by acoustical feedback.
The handset has a microphone and a little ear-speaker. The phone amplifies the microphone's signal and gives a little to the ear-speaker so you can hear how loud you are speaking, called "sidetone". You make a sound coupler with your hands to feed sound from the ear-speaker to the microphone and the gain from the amplifier makes it oscillate. The people on the phone also hear it but their phone limits the volume. They cannot block it because it could occur at any frequency, then their filter would also block voices.

It is legal as long as the sound doesn't swear or make racist remarks. I don't know if it would be legal for the sound to make a pass at a woman or talk anout religion and politics. ;D

[Guest nanop]

Know any circuits that could be connected to the phone line. When u turn it on, it would produce a sweep (sound), or a very loud, high pitch sound. (doesn't mattter what kind of waveform)

-Thanks :)

[audioguru]

A telephone doesn't produce a loud sound.
A telephone line doesn't pass high pitched sound above about 3kHz. I measured phone lines that were flat to about only 800Hz and down 14dB at 3kHz. The phone company showed me that it met their spec's. -7.5dB at 3kHz one-way into their equipment is their limit.

[Guest nanop]

Do u know of any circuits that could be connect to a phone line to produce a tone(harsh, high one?), or a sweep (sound +/- from one tone to another)?

[audioguru]

Do u know of any circuits that could be connect to a phone line to produce a tone(harsh, high one?), or a sweep (sound +/- from one tone to another)?

I answered you already. Nobody ever wanted to make noises on a phone line.
You could make a circuit to connect a tone to a phone line but it won't be very loud because the phone system and phone at the other end limits the volume.
It won't be a harsh high tone because a phone line doesn't pass it.
You could make a tone sweep its pitch like somebody singing.