Method of recovering speech path of pre-engaged call on restarting keyphone exchange system

Abstract From the Canadian patent

A method of recovering a speech path of a pre-engaged call on restarting a keyphone exchange system from occurrence of a system failure. The method includes the steps of initializing all hardware and all software except for a subscriber's table buffer of said keyphone exchange system when being generated a predetermined restarting signal of said system; initializing a variable number of port in the communication control software as a given initial value; generating an address of a port number corresponding to said variable number of port in said subscriber's table buffer; checking whether a talk bit of a line status word in a port corresponding to said port number is set or not, said line …