This circuit was found in a Popular Electronics of the 1990s. The sensor is a rotating mechanical system with a propeller-driven magnet to count pulses with a reedswitch.
This experimental AM radio circuit was found in a 1979 English magazine. It can be fitted with a...
This is a variation of the two previous circuits but controlling two LEDs. The brightness of the...
This circuit is the receiver for the CB13997E. The transistor can be the BC548. We also found this...