VARIABLE LENGTH BACKPLANE BUS

Presently available printed wiring board backplanes are wired at the time of manufacture to enable only a fixed number of groups of circuit boards to communicate with each other. This prevents a backplane from having the capability of serving a varying number of groups of boards. The present invention enables a backplane to have the capability of serving a variable number of groups of boards. Each backplane of the present invention comprises backplane bus conductors (114-125) and board conductors (226-231). The boards are effectively a part of the bus. The use of a first type of board (201, 203, 205, 207) in a backplane connector (101, 103,105,106,107) continues the bus to the adjacent connector. The use of a second type of board (204) terminates the bus and does not extend it beyond the connector (104) into which the second type of board is inserted. This permits a group of boards comprising one board of the second type and one or more boards of the first type to communicate with each other. The invention also permits communication to continue within a group if a board of the first type is removed from its connector. The invention advantageously permits the backplane to be reconfigured in the field by merely rearranging the boards.