This circuit was found in Motorola's 1967 documentation. The circuit makes use of power transistors of the time. For pulse pickup an appropriate pickup coil is used.
This circuit found in Popular Electronics from July 1974 consists of an oscillator that sends its...
This circuit was obtained in a Popular Electronics from the 90's. The gain depends on R4 and R3....
This circuit was obtained in a 1977 technical documentation. The sensor is a thermistor from 10k...