Fire detector cable

Claim 1

A RESISTANCE-TYPE TEMPERATURE-RESPONSIVE CABLE OF INDEFINITE CONTINUOUS LENGTH COMPRISING AN IMPERVIOUS METAL SHEATH AND A SPACED METAL CENTER WIRE HAVING OXIDIZED SURFACES, MEANS SEALING SAID CABLE AT THE ENDS, A TEMPERATURE-RESPONSIVE MATERIAL FILLING THE SPACE BETWEEN SAID SHEATH AND CENTER WIRE, SAID MATERIAL COMPRISING PREDOMINANTLY AN ELECTRONIC NON-STOICHIOMETRIC OXIDIC SEMICONDUCTOR TENDING TO RELEASE OXYGEN WHEN HEATED AND TO RECOMBINE WITH AVAILABLE OXYGEN WHEN COOLED AND HAVING A TEMPERATURE-RESPONSIVE CHARACTERISTIC DEPENDING ON THE PERCENTAGE OXYGEN CONTENT THEREOF, SAID SEMI-CONDUCTOR BEING SELECTED FROM THE GROUP CONSISTING OF THE OXIDES OF CO, MN, CR, NI AND CR, SAID SEMICONDUCTOR COMPRISING A PLURALITY OF SEMICONDUCTIVE METAL OXIDES OF THE SAME METAL, SAID OXIDES HAVING DIFFERENT PERCENTAGE OXYGEN CONTENTS AND BEING IN A FINELY MIXED PULVERULENT STATE COMPACTED IN SAID SHEATH INTO AN ESSENTIALLY SOLID MASS SUBSTANTIALLY IMPERVIOUS TO DIFFUSION OF RELEASED OXYGEN GAS THERETHROUGH WHEN THE CABLE IS HEATED.