A telephone exchange system useful for a dealing speech system or the like is disclosed, which can accommodate large numbers of lines (or trunks) and permit improvement of the reliability and call connection processing capacity. The system comprises exchange sub-systems A (EX-A) and B (EX-B) capable of independently executing an exchange operation and each accommodating a terminal. The terminal has a speech channel switch for connecting a speech channel including a handset to either exchange sub-system A (EX-A) or B (EX-B). When the process of connecting a call is brought about in the terminal, it selects one of the exchange sub-systems and controls the speech channel switch for connecting the call to the selected exchange sub-system.