This windshield wiper timer was obtained in an 80's Hands On. The transistor can be the BC548 and the relay is 12 V sensitive. The time is set to R3.
We found this configuration of band rejector filter or band rejector with operational 741 in a...
This oscillator can use any CMOS inverter. The circuit is crystal controlled and was found in the...
This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital...