Operating temperature: 0-50 °C. Functions of the clock The radio controlled clock of Braun ABR 314 df is set and controlled automatically and absolutely accurately by the long wave radio signal of the German time transmitter DCF 77 (Central European Time). The transmitter is situated in Mainflingen, 24 km south of Frankfurt/Main. The DFC 77 transmitter uses the caesium atomic clock of the Federal Physical Technical Institute in Brunswick as its time source. Reception of the radio controlled