This circuit was obtained in an 80s documentation on telephony. The components used are TTL, and the power must be made with 5 V.
This trip switch circuit was found in a Popular Electronics from the 90's. The frequency basically...
This audio-driven relay was published in the July 1977 issue of Radio Electronics magazine. The...
This circuit is from an 80's documentation. Equivalent transistors can be used. The circuit is...