IBM 727, Руководство по инструкции

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Temperature variations are secondary in comparison to humidity. If the tape is
stored at about 70°F, no departure from the specified width should be observed. See
6.0 "Tape Handling.”
2 .4 CAPACITY AND SPEED
It is possible to write information in any of seven tracks across the face of the
tape. Each track is independent of every other track and is associated with one read-
write coil. Looking at the top of the tape, the tracks appear sim ilar to Figure 1.
The tape is fed through the machine at a speed of 75 in ch es/sec. and the bits are
written approximately every 67. 2 usee. This means that about 200 bits may be
written in one inch of space. One 2400-foot reel can contain the information on about
20, 000 80-column cards.
Information may be placed on the tape in any configuration of bits desired. The
configuration and interpretation is under control of the external circuitry to which the
tape is attached.
The distance required to start and stop the tape motion must be mentioned when
considering capacity. The combined distance required to stop and restart the tape
motion is about 3 /4 inch. Nothing may be written in this space because the tape is
not moving fast enough to allow accurate writing or reading of bits. Therefore, the
number of stops necessary during writing greatly affects the amount of space avail­
able for writing information.
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