Key telephone system with multiple processor control

Abstract

A key telephone exchange system comprises office line units connected to office lines, terminal units respectively connected to key telephone sets and a main control unit for changing connections between respective office line units and respective terminal units. Each office line unit comprises a first memory device to store data transmitted between the office line unit and an office line, and a first processor for writing and reading data into and out of the first memory device for controlling origination and call requests to and from the office line. Each terminal unit comprises a second memory device adapted to store data transmitted between a terminal unit and a key telephone set, and a second processor for writing and reading data into and out of the second memory device for controlling transmission of data between a terminal unit and a corresponding key telephone set. The main control unit comprises a third memory device for storing states of use of the terminal unit and of the office line unit, and a third processor which sequentially scans data in the first and second memory devices of the terminal unit and of the office line unit and for exchanging connections between the terminal units and the office line units according to data obtained as a result of the scanning.