Patent ID: 8190178

Claim:
A method for using a cellular phone which is registered to a base transceiver subsystem for a wireless office system (WOS) being connected to a private branch exchange for internal telephone exchange, has an internal telephone number, and operates as an internal phone within a cover area of the base transceiver subsystem for the WOS by inputting a dedicated special number and an extension number, the method comprising the steps of: preparing a conversion table including information for converting the dedicated special number to an external phone number of the private branch exchange; preparing a region for storing the extension number entered by a user following to the dedicated special number, storing the extension number in the region in response to input of the dedicated special number and the extension number; establishing a speech path, in a case where the cellular phone is located within the cover area of the base transceiver system, via said base transceiver subsystem for the WOS and said private branch exchange; and in a case where the cellular phone is located outside of the cover area of the base transceiver system for the WOS, receiving a response which indicates not connectable from a mobile switching controller in response to the dedicated special number, converting the dedicated special number into the external phone number with reference to the conversion table, transmitting the external phone number to the mobile switching controller, and transmitting the stored extension phone number in response to connecting to the private branch exchange.