Busy test arrangement for a telephone switching network

Claim 1

IN A SWITCHING NETWORK OF THE TYPE COMPRISING A PLURALITY OF INPUT CIRCUITS, A PLURALITY OF OUTPUT CIRCUITS, AND A PLURALITY OF CHANNELS EXTENDING BETWEEN EACH INPUT CIRCUIT AND OUTPUT CIRCUIT, AND WHEREIN EACH CHANNEL COMPRISES A PLURALITY OF SWITCH MEANS SERIALLY INTERCONNECTED BY A PLURALITY OF CONDUCTING LINKS WHEREBY THE VOLTAGES ON SAID LINKS ARE DEPENDENT UPON THE FREE AND BUSY STATE OF THE RESPECTIVE CHANNEL, MEANS FOR DETERMINING THE STATE OF SAID CHANNELS COMPRISING A PLURALITY OF GATE CIRCUIT MEANS EACH HAVING A CONTROL TERMINAL, MEANS CONNECTING EACH SAID LINK TO THE CONTROL TERMINAL OF A SEPARATE GATE CIRCUIT MEANS WHEREBY THE VOLTAGE ON A LINK CLOSES THE RESPECTIVE GATE CIRCUIT MEANS IN ONE STATE OF THE RESPECTIVE CHANNEL AND OPENS THE RESPECTIVE GATE CIRCUIT MEANS IN THE OTHER STATE OF THE RESPECTIVE CHANNEL, A PLURALITY OF DEVICES HAVING FIRST AND SECOND DETECTABLE STATES, DIRECT CURRENT CONDUCTIVE MEANS FOR CONNECTING EACH GATE CIRCUIT MEANS TO A SEPARATE ONE OF SAID DEVICES FOR CONTINUOUSLY DRIVING THE RESPECTIVE DEVICE TO SAID FIRST STATE WHEN THE RESPECTIVE GATE CIRCUIT MEANS IS CLOSED, MEANS FOR DRIVING THE DEVICE TO SAID SECOND STATE WHEN THE RESPECTIVE GATE CIRCUIT MEANS IS OPEN, AND MEANS CONNECTED TO SAID DEVICES FOR DETECTING BY COINCIDENCE THE FREE AND BUSY STATES OF SAID CHANNELS.