| 摘要 |
PROBLEM TO BE SOLVED: To provide a telephone system capable of suppressing an EMI noise generated from the propagation of a high-speed digital signal to a circuit block on which a circuit component is not mounted among a plurality of circuit blocks formed on a printed board. SOLUTION: The telephone system which changes the number of trunk lines or the number of extensions to be housed by forming a plurality of extension interface circuitry or circuit blocks 1-4 of trunk line of the same configuration on a printed board, and changing the number of circuit blocks on which a circuit component is mounted among a plurality of circuit blocks, has a configuration for separating circuit blocks 3, 4 on which the circuit component is not mounted from the wiring pattern PA of a high-speed digital signal formed on the printed board. The EMI noise generated from the wiring pattern is suppressed by preventing the propagation of the high-speed digital signal to the circuit blocks on which the circuit component is not mounted.
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