Treble control (CB8721E)

This circuit found in a 1993 Electronics Hobbyst Handbook has a very simple configuration that can be used on most audio amplifier inputs.

Light Sensor Preamplifier (CB6434E)
Found in a 1990s American technical brochure, this circuit is intended for alarms that use as...
Moisture Detector (CB5367E)
We found this circuit in an 80's Radio Shack publication. The circuit uses a company buzzer, but...
TTL Oscillator (CB6150E)
This oscillator can generate 2 to 10 MHz signals and was found in an American 1980s documentation. The...