This circuit was published in an article in Radio Electronics magazine in October 1988. It uses components that are still common today, except for the sensor, which is a special type from that time.
The circuit shown in the figure generates a rectangular signal whose frequency depends on C1. For...
This voltage regulator for low current applications (a few milliamps) is from a European...
This circuit was found in a Popular Electronics from the 90s. The circuit uses TTL technology and...