A new electrolytic selenium photo‐cell is described and its characteristics given as a function of operating voltage, temperature, external resistance, and time. Data are included indicative of its response to unmodulated, modulated, and monochromatic light; comparison is made with cells of similar type or possessing similar characteristics; and a method of compensating for the dark current of photo‐cells is shown.An electronic circuit is also described which can greatly improve the voltage output of the photo‐element. It is generally applicable to photo‐conductive and photo‐voltaic cells.