P. b. x. trunk circuit for restrictor

Claim 1

IN AN AUTOMATIC TELEPHONE SYSTEM INCLUDING A PRIVATE BRANCH EXCHANGE FOR EXTENDING CONNECTIONS BETWEEN STATIONS IN THE EXCHANGE AND A TRUNK CIRCUIT HAVING A DIRECT CURRENT COMMUNICATION PATH, A FIRST SWITCHING MEANS OPERATIVE TO SEIZE SAID TRUNK CIRCUIT AND EXTEND A CONNECTION OVER A CALLING LOOP FROM A CALLING STATION TO SAID PATH, A SECOND SWITCHING MEANS INCLUDING SAID TRUNK CIRCUIT OPERATIVE RESPONSIVE TO EXTENSION OF A CONNECTION OVER SAID FIRST SWITCHING MEANS TO SAID PATH FROM ONE OF SAID STATIONS TO EXTEND SAID PATH TOWARD A SECOND EXCHANGE, AND MEANS IN SAID TRUNK CIRCUIT INCLUDING A FIRST SWITCHING MEANS AUTOMATICALLY OPERATIVE TO RELEASE SAID TRUNK A PREDETERMINED PERIOD AFTER INTERRUPTION OF SAID CALLING LOOP AT SAID STATION, AND A SECOND MEANS FOR MAINTAINING SAID FIRST SWITCHING MEANS OPERATIVE TO EFFECT SAID RELEASE EVEN IF THE CALLING LOOP IS RE-ESTABLISHED FROM SAID STATION TO THE TRUNK CIRCUIT DURING SAID DELAY PERIOD.