Abstract: A single subscriber multiple set top boxes linkage device has a real time video and audio compressor which provides a digitized payment signal, a subscriber management unit providing a subscriber pairing signal to a linkage control unit, which is responsible to the pairing, and a multiplexer. The set top boxes are classified as a master and at least two slaves. The master emits linkage control signals continuously to assure whether the pairing is correct. When the slave receives the linkage control signal, it is contrasted with the clock from the head end to assure a correct pairing. The mounting work is convenient without necessary to further add control signal wire or other dedicated accessories. Therefore, the cost is low. Moreover, a dynamic encryption is used in the present invention, which is highly reliable in safety and is very difficult to be decrypted.