This circuit is from a 1968 Electronics World. It acts directly on a high voltage alternating current relay. The sensor can be a common LDR.
This circuit was obtained in a Popular Electronics of the 90s. The circuit is compatible with...
This is a circuit that appears several times in this section and in articles. It is a preamplifier for...
Found in a Hands On Electronics of the 80s, this circuit makes use of an integrated circuit of the time...