This transistorized siren was found in the patent section of Radio Electronics magazine from March 1968. The circuit uses components from the time and has a very elaborate configuration.
Placed near a telegraphic transmitter (CW) and with a small antenna or pickup, it reproduces the...
The LM387 integrated circuit used in this project is not very easy to obtain. The circuit, from an...
The recommended distance between the emitter and the sensor of this coupler is 15 mm. The circuit is...