This filter configuration used in telecommunications uses 4 Jaumnann crystals that are interesting for low and medium frequencies. The circuit is from an 80's documentation.
This circuit, found in a 1986 documentation, uses an optical sensor to count pulses and, in its...
This different alarm system, found in an old publication, uses the starter chain to protect the...
This circuit was obtained from an American publication of the 80's. The integrated circuit is of the...