Today we have more compact solutions. This is from a Radio Electronics magazine from October 1990. It uses the technology of the time.
This 9-pixel circuit has been implemented with 9 LDRs and can be coupled to a processing system for...
A configuration that can be used to do frequency division, and that uses only a current amplifier, is...
This touch switch is from a 1978 publication. The circuit should not be powered by a...