We found this circuit in Radio Electronics from the 90s. The components are current. The sensor is a common general-purpose transistor. The connection to the sensor is made by twisted pair.
This circuit turns on a lamp after the time set on the potentiometer. The circuit is from a Radio...
This signal amplifier for ATV in the 427 to 439 MHz band was found in a magazine 73 for radio...
This amplifier has a few Watt output, using old transistors. The speaker is 45 ohms, but with...