Abstract: An invisible light communication system can communicate using infrared or ultraviolet light signals to provide more secure communications. The system includes a software definable and hardware configurable transmitter that uses an input, an encoder, an invisible light source, and an optic to transmit an invisible light signal. The system also includes a software definable and hardware configurable receiver that receives the invisible light signal using an optic, a detector, a detector, and an output. Applications for the invisible light communication system include fixed, deployable, vehicle, and wearable configurations for voice, video and data transmission and receipt in support of a variety of use cases: remote sensing; data exfiltration; remote control, ordnance detonation; tactical chat/messaging; point-to-point and point-to-multipoint audio communications; and full motion video.

Abstract: A combined unloading, relief, and load compensating valve has a poppet controlling flow between an inlet and an outlet and is spring biased to closed position. The poppet has a piston slidable in a cylindrical chamber in which the hydraulic pressure may be remotely controlled. The poppet is exposed over a small differential area to inlet pressure tending to open the poppet. The poppet and the piston are constructed as a cartridge which contains a second poppet valve and piston also controlling flow from the inlet to the outlet and is spring-biased to closed position, but openable by inlet pressure acting over a small area and the piston of the second poppet has approximately the same small area. Both pistons are connected to the common control passageway and the relative areas and spring bias forces are such that the first poppet acts as an unloading valve opening only when the control pressure is near zero and the second poppet acts as both a load compensator and a maximum pressure relief valve.

Abstract: A directional valve for hydraulic power transmission systems of the closed center type has a spool for directing fluid from inlet to either of two motor ports through one or the other of a pair of check valves for holding the load against dropping. A second pair of check valves connect from each motor port directly to a fluid return port independently of the spool. The second check valves have control chambers the maximum pressure in which is limited by a pilot relief valve to cause the check valve to act as a maximum pressure limiting valve for its motor port. A small pilot piston responsive to operating pressure in the opposite motor port can mechanically open the pilot relief valve thereby causing the second check valve to act as a counterbalance valve to prevent the motor from being driven by an overhauling load.