| 摘要 |
PROBLEM TO BE SOLVED: To use a small inexpensive positive temperature coefficient thermistor by reducing required withstand pressure for the positive temperature coefficient thermistor as an overcurrent protective element provided in a protective circuit. SOLUTION: Diodes 30, 31 are connected with positive temperature coefficient thermistor 26, 28 in series, between communication line side input terminals 22, 23 and protected apparatus output terminals 24, 25.
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