| 摘要 |
A protector for protecting equipment, especially telephone equipment, against high voltage and/or current surges such as are caused by lightning in the vicinity of the equipment or the cables to which it is connected, comprises one or more overvoltage protectors (42, 58; 234, 236) mounted upon one face of an insulating support (18; 218). A generally planar contact member (62; 290, 312) mounted upon the support member has a ground contact member (90; 296) to make contact with a ground electrode (114; 310) in the equipment to be protected and with each overvoltage protector. A spacer (60; 320, 322) of fusible plastics material coupled thermally to the protection device melts when a sustained fault occurs. As the spacer melts, it permits an electrical connect tion between the contact member and the line to which the overvoltage protector is connected, effectively short-circuiting the line to ground. Overcurrent protection may be provided by means of a resistor (116) disposed in series with the line and located close to the plastics spacer so as to heat the spacer when an overcurrent occurs. In one case, the spacer comprises a film (60) interposed directly between a pair of contacts (40, 74') which serve to shortcircuit the protector. In another case, the spacer comprises a limb (324) with relatively thin lateral projections (328, 338) which melt and shear. In both cases, the spacer preferably comprises high density, high molecular weight polyethylene.
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