The buildings have been given listed status by Historic Scotland ahead of being phased out over the next 15-30 years.
Scotland’s 74 signal boxes - 41 of which are now listed - will be replaced by two signalling centres covering the whole country.
The newly-listed ones include Corrour, which was seen in the 1996 film starring Ewan McGregor.
It was built in 1894 by the West Highland Railway Company to serve a sporting estate, whose owners ordered changes to the design to complement the adjacent waiting room.
Other signal boxes being listed following a joint review with Network Rail include Dunkeld, built in 1919, and Waverley West in Edinburgh, from 1936, which were given B status, for being of regional importance.
Signal boxes at Annan (1876) and Dumfries (1957) were also B listed, as part of the adjoining stations. Annan’s is the oldest on a working line.
Those given C listing, because of their local importance, were Dalmally (1896), Corrour, Rogart South (1894) and Elgin Centre (1888).
New uses are being sought for the signal boxes, ten of which have already closed.
Some have been transformed into waiting rooms and heritage centres, with plans for cafes and offices at others.
The news came as Historic Scotland published an online guide to the country’s signal boxes to highlight their importance to its railway history.
Elizabeth McCrone, its head of listing, said: “These purpose-built buildings are found in our towns and cities as well as some of the most picturesque parts of the countryside.
“To many, they are much-loved and instantly recognisable remnants of the bygone era of steam travel, as unmistakable in the landscape as lighthouses.
“Some of these boxes have been in operation since the 1870s but, sadly, many of them will become obsolete in the near future.
“By reviewing them for listing, we hoped we could help them receive some of the recognition they richly deserve.”