Abstract: Disclosed is a platen cover for a copying machine in which the bound volume copying platen is not used for sheet document copying. The cover includes a sheet document transport and handling mechanism with the cover having an independently liftable lid to provide access to the transport and handling mechanism. Substantially uniform counter-balancing of the cover, containing the transport and handling mechanism, or the lid alone, from the closed hold-down position to the raised stay-open position, is provided by a torsional helix spring positioned about the pivotal axis of the lid counterbalancing the lid, and a gas spring acting on the transport and handling mechanism through a lever arm about the same axis, counterbalancing the mechanism.

Abstract: A circuit for compacting variable length data words into a fixed word length format is disclosed. Each variable length data word and its associated leading 0's are separated by a delimiter bit and stored in memory. When the memory is accessed, the output word is loaded in parallel into a first shift register and shifted to strip the leading 0's and delimiter bit. The remaining data bits are then shifted serially into a second shift register. When the second shift register is full, the resultant fixed length data word is latched out. When the first shift register is empty, the next word is loaded in from memory. In this way, a series of variable length words may be compacted into a series of fixed length words. This circuit is useful for compacting variable length Huffman codes since the boundaries between codes are self evident. This circuit can also be used as a character generator, where the variable length data output comprises the bits required to generate a character image on a raster scanned display.