Basics of Railway Signalling - Absolute Block - Easy to understand!

Yes, a good video but it is important to remember that the actual rules can vary between different railway systems and different countries. The video was showing the UK signal system.

Here in the state of New South Wales distant semaphore signals, for example, had the same shape as those in the UK (fish tail at the end) but are painted red with a white chevron, not yellow with a black chevron. In their operation they were normally locked to the next home signal only, and not to the 2nd home and section signal as well as shown in the video. As a result they only indicated the state of the next home signal.
I model the Uk pre-grouping era so distants are red with a white chevron for me too. The other thing to remember is that Trainz hasn't read any signalling manuals or rulebooks so it does its own thing.
I don't know if the ones from my country (Indonesia) could be added to this topic, but I would explain how the system in Indonesia works. Here I uses the mechanical signals (Siemens & Halske type) that dates back to Dutch East Indies period as the example for the explanation :

(all photos taken from Wikipedia page for signalling system in Indonesia, which is unfortunately only available in Indonesian language)

1. Starter signal (Indonesian : sinyal keluar)

Generally it consists of a single semaphore that works like the Upper Quadrant variant of mechanical signals in UK, but with the semaphores are painted in plain red with yellow color for lens holder part (front) and yellow with black diagonal stripes (rear). On the other hand, the pylon is painted with black and yellow color, which also applies to color light signals in Indonesia. Due to the abolition of lantern for showing night aspect on mechanical signals, the night aspect lenses are largely removed, and the front part of semaphore is painted with reflective paint.

The first image below here is showing "clear" aspect for starter signal, while the second one showing "stop" aspect.



2. Home signal (Indonesian : sinyal masuk)

The current standard form of mechanical home signals have 2 semaphores (both of them are Upper Quadrant), with the upper is for straight path and lower is for diverge path. In the past, however, branch lines with light traffic were having home signals with only one semaphore and no starter signals at all.

First image below here shows "clear for straight path", whereas the second below shows "caution, entering diverge path", and the third ones shows "stop" aspect.




3. Distant signal (Indonesian : sinyal muka)

Unlike starter and home signals, distant signals are normally set in lower quadrant position (first image below) for warning trains tha they have to "prepare to stop at home signal". But when the signal changes into "clear", it would shows upper quadrant position (second image below). The shape of semaphore itself is slightly different; starter and home signals would have rounded end, while distant signal have square end (like British home signals).




There is a video that shows how the signalman of Indonesian Railways operates the Siemens & Halske mechanical signal, complete with its electromechanical interlocking device :

The video itself was taken by Mr. Ahmad Kosim, the signalman in charge for signal tower "A" of Cibatu station in West Java province.