Kokusai Denshin Denwa Co., Ltd.

Tamura Electric Works, Ltd.

Hideyuki Oikawa

Nobuo Suzuki

Shigekazu Sakata

Junichi Muroi

Tatsumi Takagi

Osamu Kai

A public telephone system includes public telephone sets assigned with different specific numbers and allowing speech communication using cards and a center apparatus connected to the public telephone sets through a telephone line. The center apparatus includes a list number forming unit for forming one list number from numbers of a plurality of invalid cards produced by illegally rewriting the cards, a registering unit for registering each formed list number in association with a series number, management number, and telephone number of each of the telephone sets, a storage unit for storing the list number and the series number, management number, and telephone number of each telephone set, all of which are registered by the registering unit, and a list number transmitting unit for calling, through the telephone line, each public telephone set corresponding to the telephone number registered in the storage unit and transmitting a list number corresponding to each telephone set. Each public telephone set includes a controller for controlling on the basis of the list number whether speech communication is allowed in use of a card.

Public telephone system

A public telephone system includes a plurality of public telephone sets and a center apparatus. Each public telephone set includes a memory for storing a current tariff table used in the speech communication service and a revised tariff table including the tariff information from the center apparatus, a first timepiece unit for setting the time information from the center apparatus to perform a time counting operation, a first data memory for storing the change time information from the center apparatus, a determining unit for determining whether a current time counted by the first timepiece unit reaches a change time stored in the first data memory at a time of call originating, and a tariff processing unit for referring to the current tariff table in the memory to perform the tariff processing when the current time does not reach the change time and referring the revised tariff table in the memory as the current tariff table to perform the tariff processing when the current time reaches the change time on the basis of an output from the determining unit.

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Saitama, Japan

Hideyuki Oikawa