How can you continuously generate a tone for a certain duration?
I would use two 555 timer ICs. Hook the first one up as a
monostable multivibrator and the second as an astable
multivibrator. The first one sets the length of duration and the
second sets the frequency of the tone. Go to your local bookstore
and get a copy of "IC Timer Cookbook" by Walter G. Jung. This is an
excellent book and will describe the pinouts and methods of