IBM 726

The IBM 726 was IBM's first magnetic tape unit. It was a dual magnetic tape reader/recorder developed for use with the IBM 701 and announced on May 21, 1952. This model of tape unit was shipped with the IBM 701 from December 20, 1952 until February 28, 1955.[1] Unlike later IBM 7 track drives, the 726 could read backwards as well as forwards.^[citation needed]

The tape had seven parallel tracks, six for data (called a copy group, not a character) and one to maintain parity. Tapes were recorded in odd parity, to ensure at least one bit transition per copy group as well as for error checking. [2]

The 726 concurrently handled two reels of tape, and there were two 726 units in an IBM 701 system. [3]

Tracks	6 Data, 1 parity
Copy groups/inch	100 copy groups/inch
Tape speed	75 Inches/sec
Transfer rate	7500 copy groups/sec
End of record gap	1 Inch - 100 chars - 16.67 words
Start time	10 ms
Stop time	10 ms
Width of tape	1/2 inch
Length of reel	1 200 feet
Composition	Cellulose acetate base

References

1. Bradshaw, R.; Schroeder, C. (June 10, 2003). "UniRecovery Fifty years of IBM innovation with information storage on magnetic tape". www.unirecovery.com. Retrieved 2019-07-13.
2. Innovations in the Design of Magnetic Tape Subsystems (PDF)
3. IBM 726 Magnetic tape reader/recorder