This circuit uses a 555 (according to the diagram) to generate 50 ms tone bursts at a frequency of 1.5 kHz. The circuit is from an 80's Electronic Design.
This excellent circuit came out in a Japanese publication from 1971. It uses Japanese transistors of the...
This circuit is from the owner's manual of the integrated circuits used. The manual is old, which...
We found this circuit in an English documentation from 1995. The Hall sensor used is from the time...