This circuit was obtained in a Hands-On Electronics from the 90's. The circuit turns on one LED at the end of the timer, erasing the other. The timing can be increased by increasing C1.
This small locator transmitter was found in old Radio Shack documentation. The transistor could be a...
This circuit changes the actuation curve of a 47k or 50k linear potentiometer so that it becomes...
This circuit is based on documentation from the operational's own manufacturer, from the 80's. The same...