British Post Office wooden battery box, portable, containing two Leclanché cell glass jars, GPO type WK4, empty, and two dry cells, round, dated October 1954, GPO type DR2, British, 1920-1960

By the 1950s most telephone exchanges derived their power from the public mains supply and used secondary (storage) batteries as back-up in the case of a mains failure. The use of primary batteries was confined mostly to the smaller private manual branch exchanges and for an ever-diminishing number of customers’ telephones. There are many telephone instruments in SMG collections of the ‘local battery’ type but no specimens of the kinds of cells or batteries likely to be used with them. The acquisition of this example enables a more complete story to be told about the way that telephone networks were supplied with operating current before the public electricity supply was widespread and reliable.