Thiết bị & Hệ thốngCâu 335 / 521
When is a primary protector required on a communications circuit?
a.Never required
b.Where the circuit is exposed to lightning or to accidental contact with power conductors over 300 V to ground
c.Required only for indoor circuits
d.Required only for fiber-optic cable
Giải thích
Section 805.90 requires a listed primary protector where communications circuits are exposed to accidental contact with power conductors over 300 volts to ground or are subject to lightning exposure. Fiber-optic cables carry no metallic conductors, so they do not require this electrical protector.
Trích dẫn luật: 2023 NEC §805.90Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
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