The purpose of this circuit is to limit noise peaks on a radio receiver. The circuit is from an 80's documentation. The diode is commonly used and the circuit is applied to a receiver IF stage.
This LED special effects circuit was found in the February 1992 Radio Electronics magazine. The...
Found in an American publication from the 1980s, this circuit can be found in commercial sound...
Found in Philips' 90s documentation, this small source can use modern transistors like the BD135...