Abstract: A storage system, such as a read only memory, is provided which includes field effect transistors each having first and second spaced apart diffusion regions of a given conductivity and a gate electrode, with at least one of the two diffusion regions of selected transistors having a third diffusion adjacent to one of the first and second diffusion regions under the gate electrodes to provide a higher voltage threshold for the gate electrode to one diffusion than for the gate electrode to the other of the two diffusions. A voltage is applied to the first diffusion having a polarity and magnitude sufficient to neutralize or eliminate the effects of the higher threshold during a first time period and the current flowing between the first and second diffusions is sensed. During a second period of time the voltage is applied to the second diffusion and the current flow between the first and second diffusions is again sensed.