This power step for relay activation was found in the 1964 RCA transistors manual. The circuit is of the NF type and the transistors admit equivalents. R4 depends on the drive voltage.
Found in American documentation from the 1970s, this circuit employs an integrated circuit from...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
This assembly circuit using a small motor as a generator was found in Radio Electroics magazine from...