This circuit is from Motorola documentation, but can be implemented with virtually any phototransistor and any general-purpose transistor. The supply voltage can also be changed.
This circuit uses a Hall device from that time as a sensor. The circuit is from an English...
Found in Radio Electronics from the 90s, this siren finds many variations on this site. The...
This audio generator that produces both rectangular and sinusoidal signals was found in a...