British Rail Class AM1
Class AM1 was allocated to the prototype AC electric multiple units, converted from fourth-rail DC electric stock in 1952 and used on the Lancaster/Morecambe/Heysham route. This route had been electrified by the Midland Railway at 6.6 kV, 25 Hz AC, but the frequency was changed to 50 Hz in 1953 to test the prototype AM1 stock.