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 circuit was found in the January 1971 Radio Electronics magazine. It keeps the light flashing if...
This circuit is from the SGS manual of linear integrated circuits. The circuit can be implemented with...
Found in a 90s Hands On Electronics, this small preamp finds applications like microphones and other...