Abstract: A bistable solid-state device, substantially immune to long term, low level radiation comprises, in combination with memory storage elements, means comprising P-type devices responsive to enabling and disabling signals for conducting signals to and from the memory storage elements only during the presence of read and write signals, and which are substantially immune to the effects of long term, low level radiation, thereby substantially increasing the reliability of solid-state memory cells. Also provided are means for generating a control signal having first and second levels and logic means responsive to said control signals of a first level to generate and supply said enabling signal to said P-type device and further responsive to said control signal of a second level to generate and supply said disabling signal to said P-type device. Sensing means for sensing the state of said bistable memory elements during a time period between successive level changes of said control signals is also provided.