| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal switching device having high reliability. SOLUTION: A first relay 4 switches and transmits a signal of a terminal C, (1) to a terminal A, (2) or a terminal B, (3), a second relay 6 is serially connected between a make contact of the first relay 4 and the terminal B, (3) and composes a break contact between the terminal C, (1) and the terminal B, (3), and a third relay 5 is serially connected between a break contact of the first relay 4 and the terminal C, (1), operates together with a break contact of the second relay 6 and composes a make contact between the terminal C, (1) and the terminal A, (2). A switching condition confirming circuit 13 checks an action of the first relay 4 and connection conditions between the terminal C, (1), terminal A, (2) and the terminal B, (3), and a relay driving signal control circuit 14 controls actions of the first relay 4, the second relay 6 and the third relay 5 on the basis of a check result. By such a composition, oxidized compounds formed on a surface of a relay contact is removed and the surface is maintained in a clean condition, contact failure of the relay contact is prevented for a long term, and a highly reliable signal switching function can be secured.
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