The Simplex 4100-9405 is a significant improvement over its predecessor, the 4100-9403. While both models offer reliable fire detection and alarm capabilities, the 4100-9405 incorporates newer technology and enhanced features. These improvements result in better performance, increased efficiency, and easier maintenance. With the 4100-9405, you can expect advanced functionalities, improved compatibility with modern building systems, and enhanced connectivity options. Overall, upgrading to the 4100-9405 ensures a more robust and future-proof fire alarm system for your facility.