Method and arrangement for checking the operative condition of a contact matrix

Claim 1

IN COMBINATION WITH A CONTACT MATRIX ARRANGEMENT SERVING A CALCULATING DEVICE AND HAVING A PLURALITY OF INPUT LINES IN PARALLEL ARRAY, AND A PLURALITY OF OUTPUT LINES IN PARALLEL ARRAY INTERSECTING ALL OF SAID INPUT LINES WITH CONNECTOR CONTACTS ARRANGED AT THE INTERSECTION POINTS, RESPECTIVELY, AND CAPABLE OF BEING INDEPENDENTLY AND SELECTIVELY CHANGED BETWEEN OPEN AND CLOSED CONDITION, EACH OF SAID CONNECTOR CONTACTS REPRESENTING A DIGIT DIFFERENT FROM THE OTHERS OF SAID CONNECTOR CONTACTS AND COMPRISING A SINGLE INPUT LINE AND A SINGLE OUTPUT LINE, FIRST CHECKING MEANS FOR DETERMINING WHETHER ALL OF THE CONTACTS ARE IN OPEN CONDITION AND INCLUDING READ-OUT MEANS FOR INTRODUCING READ-OUT PULSES INTO ALL THE INPUT LINES, RESPECTIVELY, AND RELAY MEANS FOR CONTROLLING AN EMERGENCY CIRCUIT, CONNECTED WITH THE PLURALITY OF OUTPUT LINES AND ACTUATABLE BY AN OUTPUT PULSE APPEARING AT ANY OUTPUT LINE UPON INTRODUCTION OF READ-OUT PULSES INTO ALL THE INPUT LINES, PROVIDED THAT ANY CONTACT ASSOCIATED WITH SAID OUTPUT LINE IS IN CLOSED POSITION; AND SECOND CHECKING MEANS FOR DETERMINING WHETHER IN ALL OF SAID OUTPUT LINES AT LEAST ONE