1. 5649AB Substitution Conclusion This part is not recommended as a direct substitute. Key differences include: divergent electrical specifications (6A AC rating is slightly superior, but the 4A DC rating is lower, posing a derating risk for DC applications), incompatible panel cutout dimensions (6.50mm vs. 6.35mm, which may cause mounting play or require panel modification), different actuator plating (nickel vs. chrome, resulting in subtle visual and corrosion resistance variations), and a higher electrical endurance (50,000 cycles). The part is not physically drop-in compatible due to the mounting dimensions. Furthermore, its DC load capability is inferior. Despite the longer operational life, a design reassessment is mandatory for the panel cutout and suitability under DC operating conditions. Direct "plug-and-play" substitution is not viable.