The amplitude of the DCF77 carrier oscillation is modulated with second marks: at the beginning of each second - except for the last second of each minute to identify the beginning of the next minute - the amplitude is lowered for 0.1 s or 0.2 s phase-synchronously with the carrier oscillation to approx 15%. The remaining amplitude allows a continuous carrier oscillation to be obtained and is intended to facilitate use of the DCF77 carrier as a standard frequency signal. The variable duration of the second marks serves for binary coding of time and date.