By means of the radio clock module SIPLUS DCF 77 the official time of day of the time signal transmitter DCF 77 can be read in SIPLUS S7-200, S7-300 and S7-400; thus the existing real-time clock can be synchronised.

The time signal transmitter DCF 77 is situated in Mainflingen near Frankfort on the Main, the signal can be received within a radius of 2,000 km.