This proximity sensor was found in a 90s Popular Electronics. The base is a PLL567 that operates at around 100 kHz. The circuit operates by capacitance sensing.
We found this circuit in an American publication from the 1970s. The MC1555 is the version of the...
This circuit for FET was obtained from a 1977 Radio Handbook. The input impedance is 150 ohm. The...
This is the receiver circuit for the CB13978B, found in the same 1977 Elettronica Prática...