Stuart Johnson wrote:Well, on the GWR, and in the name of this forum, it's two words, so no apostrophe is required. I'm not sure I have ever come across any professional publication where 'box appeared.
The OP evidently prefers to treat it as one word, which I also prefer though I'm not sure why. I think two words would have been the original term, contracted in later usage but perpetuated by the sort of companies who continued to say "Tickets must be shown". But it may have been regional practice, just as some of the earlier companies talked about "Break Vans". I suspect that prior to the BBC, the only standards for the language were the King James bible and Shakespeare, neither of which would cover more modern technology.
The GWR tended to put "Signal Box" on box boards. That always seems a bit superfluous, like adding "Station" to the running in boards (they did usually say Halt though). They may have been drawing a distinction between block posts and gate boxes?
SB is the abbreviation I have generally seen used in paperwork, which I suppose implies two words..
I question how widely the term box or 'box was understood. The general public called them signalboxes, and would not recognise niceties of block or non-block status. It meant that building with lots of windows - a lever frame on the platform wouldn't count. If you look at pencilled distribution lists on old circulars they often included the words "Signal Box" in full - it seems the word Signal was also needed by those whose jobs didn't involve signalling and the box abbreviation was perhaps used only by the sort of people who ferequent this forum, ie signalmen and S&T. After all, to a porter a box meant a heavy object he had to hump about in the goods shed.