Abbreviated dial number table and special number table are provided in external memory in control unit of digital button telephone system. For each of abbreviated dial numbers, the abbreviated dial number table stores a destination phone number prefixed with a special number concerning whether notice of a call originating party identification number should be permitted. For each of destination identification numbers, the special number table stores the special number. At call origination, it is determined whether dial data is an identification number of destination or an abbreviated dial number. If the dial data is an abbreviated dial number, reference to the abbreviated dial number table is made, dial data prefixed with the special number according to the destination is read out, and sent to the trunk line. If the dial data is an identification number of destination, reference to the special number table is made, the special number registered in the table is added to the identification number of destination, and resultant dial data is sent to the trunk line. In both the case, it becomes unnecessary to determine whether notice of the call originating phone number should be permitted according to the destination, and accordingly adding the special number as occasion demands before dialing the identification number of destination.