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 simple receiver picks up local MW stations with playback on a small speaker. The antenna must...
This circuit deactivates the ignition system after a certain time when you leave the vehicle. In...
This conventional humidity or water alarm circuit was found in an English documentation from 1974....