Abstract: A switching system is disclosed for the concentration of a plurality of telephone lines onto a lesser plurality of intermediate trunks, wherein an independent processor is included at both ends of the concentrator system. These processors communicate with each other over a randomly chosen idle trunk, thereby negating the need for a dedicated communication link between the processors. Each processor controls the switching functions at its end of the concentrator, independently monitors and retains trunk status, subscriber line status and system operational status, and provides system fault detection, diagnosis and recovery including communication to maintenance personnel of trouble codes based on the detected fault and its diagnosis. Manual interaction with the system is also enabled at either end of the concentrator system via display and input/output units or remote from both ends.