This simple three-LED sensor uses an NTC at the input. The circuit is based on an uncommon integrated component today. We found it in documentation from the 80s.
This receiver for infrared remote control was found in the Philips Databook of 1990, The circuit...
Found in an English publication from the 1980s, this circuit uses components that are still common...
This circuit was found in Maxim's documentation from the 90's. The frequency of the circuit is...