In a normally black double cell, grey scale enhancement is obtained by dividing pixels in the driving cell into sub-pixels which are rotated preferably through 180\xb0 with respect to each other. In one embodiment, a bypass means for said pipeline having a bypass conduit and shut-off valve system are provided for connecting said first pressure augmenting means to the downstream portion of said pipeline via a bypass conduit. The reactive chemical unit includes a chemistry that is chemically reactive with the gaseousvaporous sterilant. The movable contact is disposed so as to roll while bridging the first fixed contact and the second fixed contact. A memory interface ensures that sufficient data for each channel is present in the data reservoir by making requests to a system’s memory based on an analysis of each channel.