1. A method of operating a programmable matrix array, comprising: providing said programmable matrix array, said matrix array including at least a first conductive line, at least a second conductive line, a phase-change memory element coupled in series with a threshold switching element between said first and second conductive lines; providing an electrical signal on said first conductive line, said electrical signal satisfying the relationship: |Vth(T)+Vh(T)|<|Vhigh−Vlow|<|Vth(T)+Vth(M)|, where Vhigh is the maximum voltage of said electrical signal, Vlow is the minimum voltage of said electrical signal, Vth(T) is the threshold voltage of said threshold switching element, Vth(M) is the threshold voltage of said memory element in its reset state and Vh(T) is the holding voltage of said threshold switching element.