This circuit is based on the light comparison of two LDR sensors. We found it in a 90s Popular Electronics. The transistor must be according to the indicator or load being driven.
The trigger element of this circuit is a neon lamp. The SCR admits an equivalent. We found it in...
This bistable with transconductance operational amplifier was found in early National...
This 1965 circuit consists of a small inverter for an ultraviolet lamp. The circuit is from a...