This circuit was obtained in an Electronic Engineering of the 90s. The operational amplifiers and the sensor are from that time. The circuit has symmetrical power supply.
An inproved version of the circuit CIR129E is shown here. The resistorR1 must be at least 5 times...
We found this circuit in an old documentation. It can be elaborated based on modern components. The...
In this circuit of a 1956 publication, the handset must be high-impedance magnetic and L1 has 200...