R4-EM - 8 Series Electronic Rotary Latch The R4-EM 8 Series Electronic Rotary Latch Series combines the efficient and robust performance of a rotary latch mechanism with simplified DC motor actuation. The R4-EM 8 Series is available with an optional door sensor, integrated connector and mechanical override bracket. Flexible, concealed installation provides vandal-resistance and accommodates a variety of cabinet designs