Abstract: A garage door operator which senses obstructions and takes corrective action before entrapment can occur. Yieldable gears are utilized as a failsafe mechanism such that when the applied torque exceeds certain limit, the gears disengage so that the garage door can be manually moved. The yieldable gears may also be disengaged by remote control or by hand. Solid state circuitry is provided to achieve soft starts and stops of the electric motor. Test circuitry is provided that tests the operational readiness of the electrical components by simulating an abnormal torque condition. During operation of the electric motor, the torque load is electronically calculated and if an abnormal torque load is encountered, the electric motor reverses direction.

Abstract: A release apparatus for selectively connecting and disconnecting a sprocket drive wheel from a driven shaft by selectively thrusting a pair of sprag pins through registering openings in the sprocket wheel and into peripheral recesses in a collar secured to the drive shaft. The portion of the device attached to the sprag pins is also attached to the drive shaft for joint rotation.