This is a circuit for receiving signals from the previous transmitter. The circuit uses a common phototransistor. It was found in the August 1984 issue of Radio Electronics magazine.
This is a circuit to measure the gain of transistors, found in a European book of the 80s. The...
Suitable for general use and alarms, this Hartley oscillator circuit from a 1960's Gernsback...
What this interesting circuit does is to warn that a note written on a paper has been removed and...