Dial unit detachably mounted on public telephone for equal access

Claim 1

A dial unit adapted to be detachably mounted on a public telephone for equal access, said dial unit comprising: keypad means for key-inputting dial digits: memory means in which area codes corresponding to specific destinations to be handled as a long-distance call, and a carrier code corresponding to a specific carrier line having a right of a carrier to each specific destination, are stored in advance; determination processing means comprising: (a) dial digit determination means for identifying either one of a "1" or a "0" as a first digit of dial digits key-input by said keypad means, or a digit other than a "1" or a "0" as said first digit; (b) dial digit storage means for temporally storing all of the dial digits key-input by said keypad means, when one of "1" and "0" as the first digit is identified by said dial digit determining means; (c) equal access determining means for determining either a coincidence or a non-coincidence of an area code part of the dial digits temporarily stored in said dial digit storage means, with one of the area codes corresponding to a specific destination stored in said memory means in advance; and (d) carrier code adding means for adding a carrier code stored in said memory means in advance and corresponding to a specific carrier line, to a front portion of said dial digits temporarily stored in said dial digit storage means, when a coincidence is determined by said equal access determining means; and transmitting means comprising: (a) first converting means for converting the dial digits, when other than a "1" or a "0" is identified by said dial digit determination means, into corresponding DTMF signals in synchronism with key input by said keypad means; (b) first speech control means for sequentially transmitting the DTMF signal converted by first converting means to a telephone line connected to the public telephone; (c) second converting means for converting the dial digits, which are temporarily stored in said dial digit storage means when a non-coincidence is determined by said equal access determining means, or the dial digits with the carrier code added by said carrier code adding means, into corresponding DTMF signals, and (d) second speech control means for sequentially transmitting the DTMF signals converted by said second converting means to the telephone line in a correct dialing sequence after a key input operation by said keypad means is completed.