This differential controller was built by Harland Engineering Company Limited and installed at the Colthrop Board Mill in 1956 in Berkshire as part of a speed interlock sectional electric drive. This is one section out of eight which would have comprised the entire electric drive.

This section is around 1250mm high, 1000mm long, and 900mm wide, and consists of a pair of controllers which would have connected to a central reference controller.

Electronic differentials are electromechanical equipment used to regulate and control wheel speeds, which is necessary when different wheels are moving at different speeds.

This is one section of a larger differential controller for motor drives installed at Colthrop Board Mill which was once the country’s largest paper and cardboard producers. The mill operated from 1956 until 2000.

It was manufactured by Harland Engineering Co. which was founded in 1903 and by 1961 were known as manufacturers of electrical machinery, centrifugal pumps, water turbines, and industrial drives, employing around 1300 people.