How do infrared transmitters and receivers work?
I’m assuming this is about IR remote controls. The transmitter modulates an IR LED to send a set of pulses to the receiver, which detects the signal and converts it back to the set of pulses. A different set of pulses is used for each function of the remote control Different manufacturers of infrared remote controls use different protocols to transmit the infrared commands. The RC-5 protocol that has its origins within Philips, uses, for instance, a total of 14 bits for each button press. The bit pattern is modulated onto a carrier frequency that, again, can be different for different manufacturers and standards, in the case of RC-5, a 36 kHz carrier is being used. Other consumer infrared protocols are, for instance, the different SIRCS versions used by Sony, the RC-6 from Philips, or the NEC TC101 protocol. .