Found in Philips' 90s documentation, this small source can use modern transistors like the BD135 for TR4 and the BC series for the rest.
This circuit appears in several versions on this site. It is designed to be used between the...
This circuit uses a piezoelectric tweeter to emit a powerful continuous sound above the audible...
This circuit is based on a Siemens S566B integrated circuit. The circuit is from a Radio...