Kokusai Denshin Denwa Co., Ltd.

Tatsuo Maruyama

Yoshikazu Ikeda

Jun Matsumoto

Hiromichi Mori

In a telephone switching system having a main-speech-path switch, connected to a plurality of subscribers and a plurality of board trunks, the connection in the main-speech-path switch is controlled as follows. In the first mode, the connection between a calling channel and one of the board trunks and the connection between a called channel and the board trunk are established through the main-path-switch, so as to selectively enable speech between an operator connected to said board trunk and one of a calling subscriber and a called subscriber. In the second mode, the connections between the calling channel and the called channel is directly established in the main-speech-path switch, while simultaneously connecting the two channels to the board trunk through the main-speech-path switch, so as to enable to monitor the speech between the calling subscriber and the called subscriber by the telephone operator. In the third mode, the main-speech-path switch effects only the connection between the calling channel and the called channel, while clearing the connection between said two channels and said board trunk. Thus, the main-speech-path switch is free from the board trunk except for the monitoring and the initial connection operation, and can increase the exchange capability.

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Tokyo, Japan

Tatsuo Maruyama