This telephone circuit was found on a 90's EDN. It keeps a flashing LED to indicate that there was a call in your absence. The components admit equivalents.
The operational amplifier used in this project no longer exists, but the circuit can be adapted to...
With S1 closed, when dark, the triac will supply the load with the power set in R4. The LDR is...
Toshiba LDO Regulators Toshiba has a wide variety of low voltage drop (LDO) linear regulators...