Universal Compatibility: This control board is not only a perfect replacement for the 50A55-843 model but also fits multiple other models including 21M51U-843, 21V51U-843, 50D50-843, 50E47-843, 50M56U-843, 50A65-843, and 50D50-842, ensuring broad application with Lennox and White-Rodgers systems. Enhanced Automatic Control: Ensures stable heating by monitoring and controlling gas burners, inducer wheels, and fans. It interprets signals from thermostats and flame sensors to start burner ignition, detect flames, and safely shut down post-operation, providing reliable heating in cold seasons. Optimized Performance Parameters: Features precise settings for various relays-valve (1.5A@25VAC), igniter (6.0A@120VAC), pilot (2.2-3.5FLA@120VAC), and circulating pump (14.5-25.0FLA@120VAC). Includes a pre-purge of 30 seconds, 4 ignition attempts, and a 300-second lockout for controlled combustion. Advanced Functionality: Equipped with core functions for controlled combustion, monitoring, adjustment, and fault detection with automatic lockout. It supports comprehensive management of fan and blower controls, heating system operations, and includes features for air cleaners and humidifiers. Simple Installation Process: Designed for easy setup, it is advised to turn off power and document wiring positions before replacing the old board. The compact design measures 6.88 inches in width and 4.83 inches in height, facilitating straightforward installation. Color: As Shown Material: Metal+Plastic Package Contents: 1*Control module 1 set of accessories