The signal box at the end of Platform 3 was opened in 1935 by the Southern Railway to replace the original, cramped London & South Western box. The earlier box was located more centrally on Platform 2. A picture of the original signal box can be found at the other end of Platform 3. It is hard to see how the original box had adequate sightlines for those working in it.
The present box is effectively built to the SR's standard design introduced in the 1920s, but as if to prove that there was no standardisation it has been provided with a roof that combines the features of hipped and gabled arrangements. Though it appears on platform level to be a single storey building it actually is built into a steep bank and has 2 storeys. Underneath the platform level are significant storage spaces. The extent of the building can be seen on the approach road to the station. This makes much of the brickwork and some of the windows inaccessible for maintenance purposes without specialist equipment
In its heyday, Okehampton could boast passenger and goods facilities, a freight marshalling yard and a locomotive shed with turntable. The box was provided with a 35-lever Westinghouse A2 frame and this must have virtually filled this moderately-sized box. This type of lever frame was introduced on railways in 1924 and the company continued to produce frames until 1977.
A drawing of the track layout diagram showing what the box was responsible for in 1965 can be found on display in the museum on Platform 2. The diagram also shows that each frame lever numbered 1 to 35 was allocated to the control of a full signal (home or distant), a ground signal or a points lever. Numbers 13, 25 & 26 were spare at that time.
The next box heading west was Meldon Quarry box (closed 1970) and then the box at Meldon Junction where the Bude branch diverted from the main line to Plymouth. The double line between Okehampton and Meldon Quarry was singled at the same time as the closure of the Meldon Quarry box.
Going east from Okehampton the next boxes were at Sampford Courtenay, North Tawton and Bow up to the once very busy box at Coleford Junction where the Okehampton and Barnstaple lines diverged. This box closed in July 1971 and although the geographical location of Coleford Junction remained, the line was worked as two parallel single tracks between there and Crediton.
The final stage in the decline of Okehampton signal box came on 10th July 1972, when the box was abolished and the Meldon Quarry line worked as a single line section between Crediton and the quarry. All signalling equipment was then removed from the box. In the Dartmoor Railway days it was used as an office.