What similarity ?, what differences ?

[Esteban]

Originally Posted by FrancoItaly

Hi All
1- 4 wires to head, red= +power, black= -power, the others not shielded then DC signals, one perhaps = V/2 power.
2- Tr coil it has many turns, then the frequency may be 1 Mhz, to the
maximum.
3- In appearance it seems that there isn't a Rx coil and the ionic sensor, located near and out of Tx coil, it's the only generator for Rx signal.
4- The loop around the head, with a single turn, it's tuned with small inductor e capacitor, then his resonating frequency is at
least 10 Mhz or more, surely a harmonic frequency of Tx stage.
5- The loop it is connected with nothing but a change in inductance
or a change in the surround electric/magnetic fields it
may change some parameters in Tx coil or in the sensor.
6- There are few electronic components, surely a transistor oscillator for Tx coil, a sensor amplifier and a germanium diode (high frequency rectifier) and IC (a DC amplifier).
Some other ideas?
Best Regards

The circuitry you can see in pics is only a part. There are main PCB into pistol box.

About point 5. the tune coil connected with nothing is an accelerator of the detection. This is not critic. The accelerator was discovered by Alonso and Toto Coronel in 1959, 60 or 61, don't remember very well. When detector use this, we say: "Totorized".