Abstract: In a cargo container lifting crane employing a lifting spreader for lockingly suspending a cargo container by means of four corner twist locks, an improved electrical interlock system for interlocking the twist lock manual control switch located in the cab of the lifting crane, said interlock system including normally closed, parallel connected proximity switches which are disposed adjacent the twist locks of the lifting spreader and which are connected to a relay whereby the relay is de-energized to close a relay circuit which supplies power to the twist lock manual control switch when all of the four corner proximity switches indicate full engagement of all twist locks into the corresponding locking parts of the cargo container. An adjustable time delay is provided between full lifting spreader engagement and application of control switch power, and a by-pass switch is provided for overriding the interlock system.

Abstract: A photographic developer turning system for periodically turning a film processing container. An electric motor connected to an output shaft is mechanically coupled to a clamp disposed about a cylindrically shaped film processing container. The motor turns the container about an axis perpendicular to the axis of the container. A cam, mounted on the shaft, opens a microswitch to interrupt the supply of power to the motor, after one rotation. A variable time delay switch connected to the microswitch permits the motor to be energized after a preselected time. After each rotation, the microswitch resets the time delay switch to zero so that the container may again be rotated after a preselected time delay.