This amplified speaker is from a Radio Electronics from September 1988. The power integrated circuit is from that time and the other components are still common today.
This circuit indicates when a 28 V lamp burns, lighting a neon lamp with higher voltage. The...
This circuit, which can be used on an optical link, is suggested by the Texas Instruments...
We found this circuit in a 1992 Popular Electronics. The circuit has an optical sensor with LED...