Electric/Electronic dry box does not require silica gel or other form of desiccant. It has an electronic drying component that maintains the relative humidity within the box (or otherwise known as the enclosure) at the pre-set level.
At the basic level (which is adequate for us photographer's usage), three options are available. 1) analog controller (setting the level by turning a knob) with analog hydrometer (the gauge which you read the relative humidity level), 2) analog controller with digital hydrometer, and 3) digital controller with digital display panel. The price goes up from 1) to 3).