This two-transistor circuit was found in the September 1971 issue of Radio Electronics magazine. The sensor is an NTC and sensitivity adjustment is via R1.
With this circuit it is possible to divide the frequency of a rectangular signal by values between 2...
This circuit, which we find in a documentation from the 70s, filters out the Ru [occurring in...
This circuit simulates the call tone of a telephone. The transducer is a high impedance capsule, and...