I wonder, how would I generate the old ringback tone of the 1970’s, the kind you would hear on a rotary dial phone? I know it’s one tone modulated by another, but what frequencies it is, I’m confused. It might be 400 modulated by 40, or 420 modulated by 40. I’m not sure. Also, what’s the best way to generate phone line noise? Examples of the ringback tone I’m talking about can be found on the following recordings at this website. http://www.wideweb.com/phonetrips
You mean the tone you hear when the far side is ringing? No. Google is your friend.
We have Dual Tone Multi Frequency (touchtone) generator. There’s an equalizer filter for the 3KHz low-pass telephone cutoff (telephone voice).
I think that’s about it.
Synthesized (so clean) phone-tones here … http://freesound.org/people/FreqMan/sounds/24371/