This circuit was found in an American documentation from the 80's. The sensor is a special integrated circuit, uncommon in our times. There are modern equivalents.
The integrated circuit 4136 consists of operational amplifiers of type 741 in the same enclosure and...
In the figure we have an active high pass filter of 100 Hz, suggested by National Semiconductor in its 1994...
According to the consulted American publication of the 1980s, a zener diode can be used for DC...