Just like to say answer which I got today for clue which was Changed at Railway Station. Answer was Tablet which appears to be something at the Signal box. I personally never heard of it .
I remember this question - I'm not surprised we couldn't find the answer. Chambers dict. doesn't list tablet as being part of a signal box. Did anyone get all the answers correct?
I'm not doing this quiz, but I have heard this term a lot. Still, I have been married to a railwayman for the last 25 years, so that might have something to do with it.