| 摘要 |
PROBLEM TO BE SOLVED: To suppress a noise due to an idle code received by ports not in use at minimum in a branch circuit having multi-inpuit ports. SOLUTION: Signals from a plurality of input ports A1-An are given to a branch circuit B, from which a sum A1+A2+...+An of the signals is outputted. In the case that only the input port A1 is in use and the input ports A2-An are not in use, An idle code is given to the ports A2, A3,... An not in use other than the port A1 that receives a signal, idle codes (I), (-I) whose code pattern are alternately positive polarity and negative polarity are assigned alternately to the input ports A2-An. The sum signal outputted from the branch circuit B is A1+(I)+(-I)+...+(I)+(-I) and components of the idle codes are cancelled together, then a noise due to the idle codes is suppressed.
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