Infra Red Remote Control
IC Op-amp 741 as main chip for Infra Red receiver and transmitter. Infra Red LED connected with SCR trigger by pulse which produced from this Op-amp 741 when the SW in close position.
The square wave pulse transmitted by the LED, and will response by the photo-transistor. At receiver module, Op-amp 741 work as the main set for driver relay.
Both modules are supplied 15V power.
[source:ElectronicsCircuit]