说明：  甲机发送循环发送数据（0-f），乙机接收数据后，若结果无误使甲乙两机在各自的BCD数码管上显示当前数据。
(A machine sends cyclic transmission data (0-f). After B receives the data, if the result is correct, both A and B machines display the current data on their respective BCD digital tubes.)