I've been looking for a sound clip as well as a circuit that would generate the sound that you used to hear in the 80s if you left your phone off the hook for an extended period of time. This is not like the current sound you'll hear, but a constant sound that would increase and decrease in frequency ad infineum.
Also they used it in the Evil Dead 2 movie as a sound effect to indiciate the main character going insane. It's a funny little sound and any help tracking down some info on it would be appreciated
What I think you are looking for is the rise and fall siren like sound of the "no such number" in the days before a recording of "the number you have reached is not in service" would play. That can be found here: http://www.telephonetribute.com/audio/nsn8sec.wav
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