Abstract: A system for exchanging digital data among a plurality of hand-held computer devices. Digital signals are written by a first hand-held device to a mini-cartridge that mini-cartridge is inter-operable among a class of hand-held devices, each of which is equipped with a mini-disk drive. A common digital data format is employed to further facilitate exchange of data between devices.

Abstract: A data storage cartridge has a recording medium and a door covering an opening in the shell. The door is opened when the cartridge is inserted into the drive and closed when the cartridge is removed from the drive. A movable member rotates in cooperation with a stationary member by a actuating arm that is coupled to the door.

Abstract: An inexpensive, uncomplicated ball throwing apparatus to huff balls for hitting and fielding which includes a frame having a front end and a back end supported by a base. The frame has a firing bar hingeably attached to the frame. A pitching armature having a cup end, a hinged mid-point and an elastic band end is coaxially connected to the firing bar at the pivot hinge. A latching mechanism automatically releases the pitching armature at a firing point and includes a latch that attaches the pitching armature to the firing bar. An elastic firing band connects the elastic band end of the pitching armature and the back end of the frame. A latch release cord connects the latch to the front end of the frame and disengages the latching mechanism to release the pitching armature when the firing bar is pulled to a firing point thereby causing the elastic firing band to force the pitching bar to pivot about the pivot hinge.

Abstract: A tool having an elongate guide blade and perpendicular head for alignment with the sides of a work piece is provided to guide a hand-operated cutting-type powered tool in making straight cuts. The head is reversible relative to the guide blade to allow use with tools which have guide structure on opposite sides of a cutting tool. The guide blade provides frictional material on its lower surface to aid positional maintenance on a work piece. A measuring device to indicate position of a tool cut is provided by a replaceable dowel that is cut off by a particular tool being used with the device.