To provide an external noise infiltration preventing device and a protector that have superior signal pass characteristics up to a high frequency exceeding 770 MHz, where a noise intruding to an output side of the device hardly penetrates an input side core wire.
A two-stage coupling transformer, consisting of a pre-stage coupling transformer 3 and a post-stage coupling transformer 4, is provided between an input terminal 1 and an output terminal 2, and the primary winding of the transformer 3 is connected to the input side, and the secondary winding of the transformer 4 is connected to the output side. Then the winding ratio of the pre-stage coupling transformer 3 is identical to that of the post-stage coupling transformer 4, and they are connected back to back.
HAYAKAWA AKIRA
SUGITA MASATOSHI
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