Sequential program control system

Claim 1

Sequential program control system combination comprising a plurality of sequential separate program control units (10, 40, 39), each having a plurality of selectable paths (1 . . . 6) from a signal train input (TC) to a signal train output (18) which are selectively enabled, and in which different paths have different signal coursing time periods, each of said separate control units responding to selectable command input data (11-14; 17') addressing at least one of a selected path in said units, said units providing outputs (15, 16) in accordance with selected command input data; means for connecting the signal train output (18) of a first one (10) of the plurality of the separate units to the signal train input of a further one unit (40, 39) of said plurality of separate units to thereby connect said units in a serial chain and enable the further unit (40, 39) when a signal train output from the next preceding unit in the serial chain is received; at least one common time delay element (37) connected in the serial chain connection of said first and further units, and adding a fixed time delay to the signals coursing in said respective paths, which fixed delay is substantially longer than the longest of any one of the signal coursing time periods through any one of said paths, to maintain approximately constant the overall coursing time of the signals through said series connection of the units regardless of the selected path of the signals in any one of the units; means connecting the signal train output of the serial chain to the signal train input of said serial chain to connect the serial chain in a closed loop having a signal coursing time therein which is essentially independent of the selected signal paths in said units, thereby forming a closed loop serial chain; and means (C) for applying cyclical signal trains to said closed loop serial chain.