Replaces #56 and #58 Digital Controls The #62 automatic digital control works like the #58 control, but can turn on your HVAC blower when there's a need for humidification, even if there's no call for heat. External blower activation relays are eliminated! The #62 automatic Aprilaire humidistat control works in conjunction with your furnace to control the operation of the humidifier. The control senses indoor RH and outdoor temperature and automatically adjusts the operation time of the humidifier to provide the optimum humidity level in the home. The digital readout on the control displays the RH level inside the cold air return. Can also be used in manual mode when it is not possible to run wire to outdoor sensor. New lighted display includes indoor relative humidity readout, service indicator light, water panel change light, and "on" indicator light. MOUNTS ON RETURN DUCTWORK Includes: * Control * Outdoor Sensor * Manual Mode Sticker * Installation Instructions * Owners Manual For use with models: 800 STEAM HUMIDIFIER Unit dimensions - 5 15/*16" W X 4 1/4"" H Requires round 3/4" hole for duct mounting.