Tape trivia/comments It seems that the way to make a really accurate tape drive, such as those used for telemetry is to have two independently controlled capstans with sensors attached to each. The "old" vacuum column tape drives were really interesting to watch as the level of the tape oscillated up and down in the column. There are some technologies used with the Omnimax movie format that might be applicable to magnetic data storage. They place timing marks along the edge of the film to allow the system to detect and correct the speed of the film. The also can digitally encode the sound along the edge of the film, there are however separate attempts to coordinate sound on a CD with the film. I read an article about how CD's are cut out from a optical tape media which has lowered the cost of manufacture. It might be neat to make a storage media that was optical tape 3 inches wide. On a slightly different topic, there were early attempts to make video tape recorders that were not helical but used 256 parallel tracks each with a separate head. You could fastforward 1 minute by switching heads. Tape handling was much simpler that with helical. There was lots of tape wear because of the number of tape passes. The heads were also expensive. I have also heard that the 4mm DAT tapes are good for about 100 tape passes, this would seem to mean that weekly backups and verifies might destroy a tape. I know that the tolerance levels are not very good, it seems to be difficult to restore on a drive different than the one that was used to create the tape. Tape standards seems to be much more vague. I remember 800 bpi 9-Track tapes very fondly. I still have several. Mike mmcfadden(a)cmh.edu