We found this circuit in the March 1995 issue of Electronics Now magazine. The circuit has a frequency range determined by C1 and R3. The signal generated is square.
This circuit from Popular Electronics powers a small speaker. The transistor can be of general use...
When the sensor X1 is opened, the relay is energized. When waiting, the current drained is very...
This circuit for measuring bridges was found in the October 1995 issue of Electronics Now...