Safety system with intermittent photoelectric beam
 A safety system for high density mobile storage utilizes a photoelectric transmitter that cyclically emits an intermittent beam at a predetermined frequency into an aisle adjacent a mobile carriage. Two or more transmitters can be arranged in each of one or more clusters on the carriage. The intermittent beams are directed to photoelectric receivers across the aisle. Each receiver sends a signal to reset an associated counter each time the receivers detect an intermittent beam. As long as every receiver detects at least one intermittent beam at the predetermined frequency, the mobile carriage is enabled to move. The receivers can be on the same mobile carriage as the transmitter to protect a vertical plane close and parallel to the front face of the carriage. 
Tab Products Company
G
G01V
inventional
David R. Thomas C.
Eaton Hartmann