Electronics giant Philips invented the RC5 protocol for controlling electronic equipment such as CD players, VCR's and audio amplifiers way back in the 1980's. The RC5 standard has been adopted and used with great success ever since, which means it is probably the most common IR remote control format in your home today. We have recently been playing around with a PIC microcontroller based RC5 decoder programmed in C, with the purpose of testing any RC5 based remote handset you may have. The image above shows the RC5 code for a button press of '1' on the CD player remote control decoded into binary and displayed on the 14 LEDS - the address data for a CD player is '20' hence the 10100 binary pattern on the green LEDS. The RC5 command for '1' is unsurprisingly 000001 in binary as shown on the red LEDS. The two start bit LEDS (yellow) are showing 11 binary and the toggle bit is off. In the pic below the '1' button has been pressed again showing the toggle bit now being set (blue LED).