This circuit is from a 1968 publication. Here we have several types of resistive sensors with individual adjustments triggering a single SCR. Power depends on the type of sound device to be triggered.
Found in a 1964 Electronic Design, this circuit protects the transistors of a complementary output stage. The...
Found in a 70s RCA manual, this circuit uses transistors from the era. Equivalent types can be...
This circuit found in a 1988 documentation consists of a timer or sequential timer controller. The...