Digitally-operating electrical equipment with counter for automatically adapting output to 50 Hz or 60 Hz input

Claim 1

Digitally-operating electronic equipment, automatically handling power-supply frequencies of 50 Hz or 60 Hz; comprising means utilizing a full wave of the power supply frequency for generating a waveform having a pulse width referenced thereto; means connected to an output of said waveform generating means for counting into a counter, from the beginning to the end of the reference pulse waveform, a sequence of pulses generated independently of the power-supply frequency and which is of an essentially higher frequency than the power-supply frequency; means connected to an output of said counter for subsequently discriminating the content of the counter at a threshold value which is associated with about 55 Hz; finally in dependence upon the obtained result, means generating a first signal which is associated with frequency of 50 Hz or generating a second signal associated with a frequency of 60 Hz generated; and a frequency divider responsive to said first or second signal for switching respectively between a dividing ratio of either 50:1 or 60:1 so as to generate at an output of said frequency divider constant frequency pulses for said digital equipment synchronized to the power supply regardless of whether it is 50 Hz or 60 Hz.