Found in a 1968 Texas Instruments documentation this circuit uses an SCR from that time. Modern equivalent types can be used for a higher power version.
This 1986 documentation circuit provides 3, 4, 5, 6 V voltages under 350 mA for powering walkmans...
This sonic control circuit for a small robot turtle was obtained in an American documentation from 1967....
This fast-acting circuit uses a 555. We found it in the November 1992 Radio Electronics magazine. The...