Crosspoint switching array and control arrangement therefor

Claim 1

IN A COMMUNICATION SWITCHING SYSTEM, A FIRST SET AND A SECOND SET OF LINKS, EACH LINK HAVING A PLURALITY OF CONDUCTORS INCLUDING AN OPERATE CONDUCTOR AND A HOLD CONDUCTOR, A SWITCHING MATRIX COMPRISING A PLURALITY OF RELAYS ARRANGED IN A COORDINATE ARRAY TO SELECTIVELY CONNECT ANY LINK OF THE FIRST SET TO ANY LINK OF THE SECOND SET UNDER CONTROL OF A MARKET ARRANGEMENT, EACH RELAY COMPRISING TWO WINDINGS, FOR OPERATE AND HOLD RESPECTIVELY, A UNIDIRECTIONAL DEVICE INDIVIDUAL TO EACH RELAY CONNECTED IN SERIES WITH THE OPERATE WINDING BETWEEN THE OPERATE CONDUCTORS OF A LINK OF THE FIRST SET AND A LINK OF THE SECOND SET, WITH THE DEVICE POLED FOR FORWARD CONDUCTION AT THE FIRST LINK WITH RESPECT TO THE SECOND LINK, EACH RELAY HAVING A NORMALLY OPEN CONTACT SET CONNECTED IN SERIS WITH ITS HOLD WINDING TO THE HOLD CONDUCTOR OF ONE OF SAID LINKS; A BUSY RELAY INDIVIDUAL TO EACH LINK HAVING A WINDING CONNECTED TO THE HOLD CONDUCTOR AND A NORMALLY CLOSED CONTACT SET CONNECTING THE OPERATE CONDUCTOR TO THE MARKER ARRANGEMENT; SAID MARKER ARRANGEMENT INCLUDING MEANS TO ESTABLISH A TEST CIRCUIT TO THE OPERATE CONDUCTORS OF A LINK OF THE FIRST SET AND A LINK OF THE SECOND SET WITH A SOURCE OF POTENTIAL PLACING THE LINK OF THE FIRST SET AT A DIFFERENT POLARITY WITH RESPECT TO THE LINK OF THE SECOND SET, DETECTING MEANS IN THE TEST CIRCUIT OPERATED IN RESPONSE TO THE BUSY RELAY CONTACTS IN BOTH THE FIRST-SET LINK AND THE SECOND-SET LINK BEING CLOSED TO