Residential Electric Door and Gate Operators Commercial-Industrial Trolley type-ceilling, Wall Mounts, B1-Parting, Sliding Doors Electric Operators Waterproof Trolley Type-Ceillling and Jack-Shaft-Wall Mount Explosion-proof Trolley Type-Ceillling and Jack-Shaft-Wall Mount Sliding Gate Electric Operators Swing Gate Electric Operators Trafic control barriers To control of vehicular traffic in private and public parking areas. Rolling &Fire Doors Rolling Service Doors & Fire Doors. Jack Shaft - Wall Mount Accessories Different accessories for your needs Safety Devices Reverse Systems and Sensor Entry-Exit Devices Loop Detectors, Card Reader and more Operating Controls   Modifications   Special applications   Fire Release Door Arm Used in conjunction with our electric door operator (models SD and BSD) for sliding or bi-part fire doors. When temperature reaches 160oF, a fusible link opens to release the spring-loaded arm from operator trolley, permitting door to close automatically by it's own gravity. This is used to prevent fire from spreading to adjacent areas. Part No. 50216