PURPOSE:To attain speech of an important person with higher priority by allowing a caller to revise priority class information given corresponding to a telephone set into a high priority class from a calling telephone set. CONSTITUTION:An identification code is designated by a command from a console or the like of a central controller 8 and stored in a storage device. On the other hand, a subscriber requesting a change of a priority class enters a predetermined identification code with a means such as a dial signal, a voice, or combination of specific tones. Then the central controller 8 collates the identification code stored in advance in the storage device with the identification code inputted from a telephone set 6 and changes the priority class of the telephone set 6 higher when the coincidence is discriminated. Thus, the priority speech is realized for the caller.
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