To provide a communication equipment, its communication system and method, and its coding/decoding method where data are transmitted at high speed for a long distance regardless of its compactness.

A coding circuit 12 of a transmission unit 1 encodes data to be sent into biphase code, applies frequency division to the obtained biphase code, and a transmission circuit 13 sends the biphase code 1/2 frequency-divided as a coded signal. A reception circuit 21 of a reception unit 2 receives the coded signal consisting of the biphase code 1/2 frequency-divided. A decoding circuit 22 detects a change in a level of the received coded signal for each prescribed period corresponding to a time width of each bit of the data, and decodes the coded signal, based on the detected level change.