The installation is an original rocker, built with a field T1 and T2 bipolar transistor effect, the whole constituting a loop amplifier itself.
A power, the two transistors are off and the relay is at rest,
By touching the plate S, the induced voltages are sufficient to lead Ti and therefore Tj, which passed over at work.
But the R point also goes high, thus maintaining conduction of the transistors, via D1 and R4 .The chain relay remains at work, even finger removed.
R1 8.2 KR
R2 1 KR
R3 8.2 MO
R4 820 KR
R5 390 KR
R6 3.3 KR
PAJ1 22 KR Hor
C1 2.2 MF
clips pile 9V
1 relais 12V 2RT
Production . Settings.
Precautions for FET deemed fragile.
P1 setting determines the system's sensitivity.