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Hi, I'm trying to find the best and simplest method of generating telephone signaling tones such as dial and busy tones.
Does anyone have any schematics.
Well, if you ask me, I'd say the easiest way of producing those signals is through an IC and a microcontroller. I guess I don't have any schematics but if you're interested in components, I bought some DTMF chips from **broken link removed** a while ago that seemed to work very well (didn't test them extensively). If your interested call progress tones though, I'd try out their **broken link removed** generator [link has .pdf], which is availible in DIP14 or SOIC16.
As far as dialing goes, I'd try thier M-8888 (8051 and i86 interfaceable), or M-8880 (for Motorola-type interfacing). Both chips were very reliable, and --if I remember right-- they even took care of that 3db "twist" between the tone pairs. Most of those parts are availible through Digikey.com. I also found some very useful diagrams for phone interfacing at this Helsinki University of Technology site.
Hey thanx alot. I will look into using that tone generator I.C that you mentioned. However, I did use 2 555 timers in the astable configuration to generate the individual tones and then used a LM381 chip configured as a mixer to mix both tones. After which I coupled the output of the mixer through a capacitor and sent it to a speaker.
The dial tone generated sounds like a dial tone, however it has a higher pitch.
I'm not really satisfied 100% with the results, so I will try your suggestion if I can source that chip.
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