Patent ID: 7053760

Claim:
An apparatus for alarming a decrease in tire air-pressure which alarms the decrease in inner pressure of the tire by using a judged value calculated based on wheel speed information obtained from tires fitted to a four-wheeled vehicle, comprising calculating means for calculating the judged value based on the wheel speed information on each of the tires, the calculating means being connected to one of on-vehicle LANs, via which the wheel speed information on each of the tires is transmitted, wherein the calculating means converts the wheel speed information into digital data and the calculating means captures the wheel speed information on each of the tires via one of the on-vehicle LANs, wherein at least a means for calculating wheel speed and the apparatus for alarming a decrease in the tire air-pressure are connected to said one of on-vehicle LANS, and said wheel speed information per wheel is 2 bytes of digital data per each wheel by using said means for calculating wheel speed, said digital data being transmitted to said apparatus for alarming a decrease in tire air-pressure via said one of on-vehicle LANs, and said wheel speed information of four wheels is captured via one transmission.