Abstract: A manually user-propelled wheelchair construction having a frame, a seat having a narrow front portion and a wider rear portion, a central axis on the seat, wheels on the frame proximate the front portion of the seat, with the wheels being oriented so that vertical planes passing through the wheels and parallel to the central axis of the seat also pass through the rear wider portion of the seat. The frame can be disassembled into a plurality of frame portions, a seat, and wheels.

Abstract: A matrix switch system is described with which a large number of communication lines can be interconnected. The lines are arranged in multiplex groups which are in turn sampled by multiplexers. The multiplexers in turn are coupled to matrix lines which intersect at connectable crosspoints. A common timing signal with a predetermined minimum number of time slices is used to reconfigure the system during each time slice and form the desired line connections through the multiplexers and crosspoints for signal transfer. A technique is described to allocate time slices for the various connections of the lines and minimize matrix lock conditions.