Found in RCA documentation from the 1960s, this 60 V regulator has a 100 V input and a current of 1 A. The transistors are from that time. One can try to use modern equivalents.
This circuit was obtained in a 1979 publication. The operational amplifier is of the type with...
This circuit was obtained in a 90’s Popular Electronics. The frequency depends on C1, a component...
Because it uses TTL integrated circuits, this siren must be powered by 5 V or as indicated with D1 to...