The Aprilaire Auto Trac humidifier control. Computer-equipped, completely automated, never needs manual adjustments. The advanced computer technology measures the outdoor temperature and indoor humidity and continually adjusts your homes indoor humidity to its optimum level.

For use with models: 110, 112, 220, 224, 400, 440, 445, 445A, 448, 550, 558, 560, 560A, 568, 600, 700, 760, 760A and 768

Includes:

• 56 Humidistat
• Outdoor Sensor
• Manual Mode Resistor
• Manual Mode Sticker
• Owners Manual and Installation Guide, Cutout Template

Unit dimensions - 6" W X 4" H
Plenum opening for unit - 4 9/16" W X 2 13/16"H

Note - replacement remote sensors can be purchased separately