This 1970s RCA circuit can be triggered by light or dark, depending on how the LDR is connected. The controlled load depends on the triac.
This is the configuration of a conventional bandpass or bandpass filter with an operational...
This Headset Coupler or Phone Patch was found in an American 1980s amateur radio documentation. The...
This circuit is from the 1983 Intersil Databook. This is a configuration that is still used today...