A data compression architecture comprises a shift register structure comprising first and second parallel paths, each comprising several shift register elements for storing previously received data characters. The upright main body includes a first housing that is installed on the wheel assembly so as to be rotatable in a leftwardrightward direction, and a second housing that is installed in the first housing so as to be rotatable in a forwardbackward direction. The inner layer also includes a plurality of interconnected channels. In an alternate embodiment of the present invention, the tensioning device includes a pair of laterally offset holes through which the lift cord extends. in the range of 30\u201345\xd710\u22127\xb0 C.