Foley & Lardner
Surge protector for telecommunications equipment
 An overvoltage protector for protecting equipment, especially telephone equipment, against high voltage 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) mounted upon one face of an insulating support (18). A generally planar contact member (62) mounted upon the support member has a ground contact member (90) to make contact with a ground electrode (114) in the equipment to be protected and with each overvoltage protector. A spacer (60) of fusible plastics material extending between the contact member (62) and an interconnection (26) to one terminal (42A) of the protector melts when a sustained fault occurs. As the spacer melts, it permits an electrical connection 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 interposed directly between a pair of contacts which serve to short-circuit the protector. In another case, the spacer comprises a limb with relatively thin lateral projections which melt and shear. In both cases, the spacer preferably comprises high density, high molecular weight polyethylene. 
Northern Telecom Limited
H H
H01C H01T
inventional inventional
Francis Y. T. William P. Paul A. James E.
Hung Trumble Taylor Anderson