Power line transient surge suppressor

In a power line surge suppressor having first and second input terminals for connection to high and low or return lines of electrical power mains, first and second output terminals for connection to loads to be protected, first and second load power conductor means coupled between said first input and output terminals and said second input and output terminals respectively for transfer of electrical power therebetween, and a first surge suppression means coupled across said first and second conductor means, said first surge suppression means having the property of presenting a reduced impedance to line voltage surges above a given threshold value so as to bypass surge currents through said first suppression means, the improvement comprising:

• thermal cut-out means having a temperature-responsive switch means, said switch means being operable from a normally closed position to a circuit breaking condition when the temperature thereof exceeds a given threshold value, said switch means being inserted in series with one of said conductor means so as to terminate said power flow when in an open condition, and a resistance heating element in thermal contact with said switch means;
• electrical current interrupting fuse means coupled to said first surge suppression means so that said bypass surge currents pass through said fuse means, said fuse means having a blowout value chosen to withstand said bypass surges and to blow only at current values corresponding to a short circuit failure condition in said first surge suppression means, said resistance element being connected in parallel to said fuse means so that upon blowing of said fuse means the current thereafter flowing through said resistance element heats said element to open said switch means.