What types of signalling systems are used on IR?
R uses several forms of signalling. In IR manuals reference is made usually only to 4 main types of systems, Lower Quadrant semaphore, Modified Lower Quadrant semaphore, Multiple Aspect Upper Quadrant semaphore, and multiple-aspect colour-light signalling. But in practice there are some variations in the kinds of colour-light signalling seen, so for ease of analysis, the following classification is used here. (Abbreviations in parentheses given for ease of reference in the text that follows.
R uses several forms of signalling. In IR manuals reference is made usually only to 4 main types of systems, Lower Quadrant semaphore, Modified Lower Quadrant semaphore, Multiple Aspect Upper Quadrant semaphore, and multiple-aspect colour-light signalling. But in practice there are some variations in the kinds of colour-light signalling seen, so for ease of analysis, the following classification is used here.
