This circuit was found in an Electronic Design from 1964. The components are from that time and can be replaced by equivalents. The modulation ranges from 0.25 to 0.75 of the 20 kHz pulses.
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...