Key controlled digital system having separated display periods and key input periods

In a digital system comprising a character display means having plural display elements arranged in digit positions respectively and energized sequentially, a digital computing module for generating a repeating sequential series of first pulses and a group of second pulses simultaneously with each of said first pulses for selective energization of said display elements, and a keyboard means having keys whose actuation effects the coupling of timing pulses to said computing module, said timing pulses being provided for the coding of information corresponding to the actuated key, the improvement wherein said computing module comprises a display timing circuit means for receiving said first pulses, said display timing circuit means being arranged for enabling the supplying of said first pulses to said display means during a first period of each of predetermined time intervals and for inhibiting the supplying of said first pulses to said display means during a second period of the predetermined time interval, and a key input timing circuit means for receiving said second pulses and said timing pulses, said key input timing circuit means being arranged for supplying said second pulses to said display means during said first period of the predetermined time interval and for coupling said timing pulses to said computing module during said second period of the predetermined time interval, whereby selective energization of said display elements is enabled during said first period and not during said second period when said timing pulses are coupled to said computing module.