What is RC5?

RC5 (Remote Control) is developed by Philips engineers and it's a protocol to steer audio/video equipment wireless by (invisible) infrared light, for example from the remote control to your TV-set.

RC5 briefly
When you push on a button from the remote control, it sends an infrared signal with the next property's to the receiver:















1 Header (startbit)
1 (extended) Commandbit <<< (inversed 1=0 / 0=1)
1 Toggle-bit
5 System bits
6 Command bits

After the start-bit comes the toggle-bit, by every push on a button changes the toggle-bit, if it was a 1 it becomes a 0, if it was a 0 it becomes a 1, etc.
On basis of this toggle-bit the receiver knows that the same button is pushed more then once.
The 5 system-bits contain the device-code that must controlled (TV, VCR1, VCR2, SAT, TAPE, etc.), so that if for example the stand-by button in video-mode is pushed, only the video goes stand-by and not even the TV or other devices.
With 5 system-bits you can control maximum 32 different (audio/video) devices.
The 6 command-bits contain the button-code which is pressed (0-9, MUTE, TXT, PLAY, REC, STOP, etc.).

The extended command-bit was earlier a part of the start-bit, but with the original 6 command-bits there's a maximum of only 64 different commands per device to send, and for a modern device, like TV and video, it's a little these days.
The Philips engineers has adjust the RC5 code to RC5X (extended), by changing to make the second start-bit also a command-bit, so that there are now 128 different commands possible.
RC5X can still control the old "normal RC5" devices (backwards compatible).
Seeing that these days 128 commands are even les, the Philips engineers developed the RC6 code.

A list with most of the RC5 system codes
A list with most of the RC5 command codes
Something about RC6 / RC6A
More info about RC5 (German language)