The transistors of this circuit found in a 1965 magazine can be the BC558 and the sensitive 12 V x 50 mA relay. The other components are common.
This circuit was found in a publication from the 50's. The circuit uses germanium transistors of...
Equivalent operational amplifiers can be used on this crystal-controlled oscillator. The circuit is...
The transmitter can be that of CB9574E. This receiver uses a PLL to directly trigger a sensitive relay....