Abstract: Circuit protection systems which comprise a PTC resistor and a second resistor, e.g. a thick film resistor, which is thermally and electrically connected to the PTC resistor have a break current I.sub.B and a hold current I.sub.H such that the ratio I.sub.B /I.sub.H is at most 20. Suitable PTC resistors are conductive polymer devices which comprise a PTC element which has been radiation crosslinked under conditions such that the average dose rate is at most 3.0 Mrad/minute or during which no part of the PTC element which is in contact with the electrodes reaches a temperature greater than (T.sub.m -60).degree.C., where T.sub.m is the melting point of the polymeric component of the conductive polymer.

Abstract: A process for preparing an electrical device which has a conductive polymer exhibiting PTC behavior. The cross-linking may be to a level of 50 to 100 Mrad or higher for devices designed to withstand high voltage test conditions. The device may be a laminar device having a center layer of higher resistivity than two surrounding layers.

Abstract: A process for preparing an electrical device which comprises a conductive polymer exhibiting PTC behavior. The device is irradiated by use of an electron beam at an average dose rate of less than 3.0 Mrad/minute. The cross-linking may be to a level of 50 to 100 Mrad or higher for devices designed to withstand high voltage test conditions. The device may be a laminar device comprising a center layer of higher resistivity than two surrounding layers.