The present invention is method of containing information state number inside signal for expanding traditional tie-station in energized tie-station. Through tristate transformation, the excessively expanded information state may be used in carrying broadcast/multicast service index, and the tristate transformation includes double phase deviation process and zero amplitude. One signal, such as fastcalling information, is selected. The subunit is then complementarily transformed. The present invention makes it possible for the energized tie-station to detect new information, such as broadcast/multicast service index, in the method compatible with traditional tie-station.