This circuit was found in a 1975 documentation. The SCR can be of any type and in this case, we have the horn activation. The relay must be a 12 V type with high contact current.
This stage with polarization of only one resistor can use any general-purpose transistor. The...
This voltage-controlled potentiometer using an LDR was found in an English documentation. LDR is...
This interesting sensor for RF signals was found in an article in the June 1989 Radio Electronics...