There are several layers of detail to be considered when examining remote control signals, each layer adding another potential degree of freedom/complexity. The design of a universal remote control device capable of dealing with all imaginable signal types would be no simple job. Fortunately, it appears that most modern remote controls adhere to certain norms, which reduces the complexity of a system such as the RedRat3 and irNetBox.

This is around 1000nm, and appears to be used by the majority of systems. Some older controls used RF instead of IR, but these are not very common. Some more recent home automation systems now also use RF remote controls due to the increasing availability of cheap RF transmistter and receiver units, and perhaps more importantly for complete home automation one is not limited to line of sight operation.

The standard is to use amplitude modulation of a bit stream using carrier frequency somewhere around 40KHz, the exact value of the modulation frequency depending upon the manufacturer of the remote control. As the signal is a bit stream, the amplitude of the carrier frequency is either maximum, or nothing!

As the RedRat3 and irNetBoxdirectly sample the raw IR signal it is capable of dealing with signals in the range from about 15KHz to 70KHz. The ability to determine the exact modulation frequency for each type of remote control improves the signal transmission reliability and range.

Once the physical transmission of information is in place, the signal coding is the next level of detail. There are a few standards, such as RC5, RC6, RCMM, XMP-1 etc. but many manufacturers implement their own codings.

Variations in signal coding include the bit rate, the signal lead in time, the number of signal repeats or the signal tail. The code itself is used in different ways, some manufacturers have a manufacturer ID, then a device address and lastly the operation itself. For a universal IR control system, it is not necessary to understand the coding, what is important is that the signal form is reproduced with the necessary accuracy.