The indicated circuit uses an unusual buffer from National Semiconductor. The frequency is given by resistors R1 and R2 as well as capacitors C1 and C2.
The circuit shown by the figure below can produce signals in the range between 20 kHz and 30 kHz....
We found this circuit in an article in Electronics Now magazine from November 1997. The circuit uses...
The figure shows how to implement an OR function with two inputs, using a relay. The relay...