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. Harland differential controller 1956
