This circuit is from a 1968 Texas Instruments documentation. The components are from the time and the sensor photodiode is difficult to obtain today. The circuit has a response from 10 Hz to 20 kHz.
This circuit, from the 90's, is intended for operation with vinyl record players of the time, as...
Using a zener diode it is possible to change the linearity of the scale of an analog instrument by...
Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime...