Found in Motorola documentation from the 1970s, the circuit presented uses a component from the era that is not common today. The characteristics of the coils are given next to the diagram.
The circuit is from the 1994 National Semiconductor Linear Applications Handbook. The component used is...
This circuit, which is present in other points of this website, was found in a 90s Hands On...
This simple circuit produces a tone when triggered by any vibration picked up by the sensor. The...