Abstract: A system is described for reliable monitoring of clock rates, where a first processor which receives a first clock rate causes a counter to count using this first clock rate. A second processor which receives a second clock rate also causes another counter to count using the second clock rate. The readings of the counters are stored by the processors at predefined intervals in a common memory. Subsequently each of the processors loads the counter reading of the other processor, and compares it with its own counter reading. If both readings are within a tolerance range, one of the counter readings is used as a reference for all the other counters and the other counter readings are made equal to this reference value, so that subsequent monitoring of the processors is based on this reference value for the respective counters. If a reading is outside the tolerance range, an error is triggered.

Abstract: An error preventing incremental measuring system utilizes a plurality of scanning elements associated to a relatively movable divided scale. But, instead of merely comparing the results of a plurality of independent channels originating at the scanning elements and terminating at separate counters, the system according to the invention combines the signals from the scanning elements by way of a logical network into a further signal similar resp. dissimilar to one or more of the scanning signals, thus avoiding the necessity of fault tolerances.

Abstract: An electronic counting system having a directional discriminator for accepting input signals representative of the count, a reversible up-down counter responsive to the directional discriminator for performing the counting function, a numerical display for displaying the value of the present count, and logic apparatus for the calculation and display of values for manual input to the up-down counter. The entry logic apparatus includes a keyboard for the manual entry of numerical data and function commands, a computer-calculator element for processing the numerical entry display for displaying the numerical data entered into the keyboard and the function results. A transfer switch applies the numerical data of the entry display to the up-down counter for setting the counter to the entry display value.