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.
This two-band receiver capable of tuning medium waves and the 3.5 to 10 MHz band was sold in Japan...
This circuit is from an American publication from 1975 and can use other operational amplifiers and...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...