The Magic of Modern Signals was a short series of articles which appeared in volume 1 of Railway Wonders of the World. Here is a complete list, with links to the full articles.

The Magic of Modern Signals

1.     The Magic of Modern Signals
2.     Ruling the Traffic Routes
3.     Automatic Safety
4.     Railway Signalling
5.     Signals and Signalling
6.     Signalling Under Grand Central Station
7.     Flashlight Signalling