The came up with this bit of code that produces two tones at a time out of two seprate pins. A lowpass filter to clean up the square wave on the pins, then mixing them togeather make the Ultimate Tone Box. You can generate any type of Multi Frequency tones you like, just change the timing parameters.
Also of interest is this pic code I found by Eric Smith. It produces DTMF tones out of 1 pin using pulse width modulation. Very interesting code.
The newest Basic Stamps put out by Parallex now have simalar routies in them as the Eric Smith DTMF code. Using these devices it should be very easy for just about anyone to built there own ultimate box. With the Basic Stamp you have the added benifit that the code can be redownloaded again and again as needed for different tone requirements.
The possibilities are endless, and less expensive that the old lower tech ways of building boxes.
Get Pics, It Pays,