This low power circuit can be powered with voltages from 1.8 V. We find it in a 80s Hands On Electronics. The load can be from 8 to 32 ohm.
The idea is simple: using a flashlight to cut your TV commercials triggers a relay that turns off...
Found in documentation from the 70s, this circuit uses an operational one from that time. It goes for...
Found in a Popular Electronics from the 90s, this circuit uses thermistors for low noise...