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Clock Track Writing

IP.com Disclosure Number: IPCOM000097235D
Original Publication Date: 1962-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Money, JB: AUTHOR

Abstract

A two-stage method is utilized to record an accurately closed clock track 11a on a magnetic record disk 11. Two read-write heads 12a and 12b are located over clock track 11a which has a radius r. The heads are spaced from each other along this track by a distance s. The separation s is chosen so that s = 2/m//f, where m is an integer and f is the desired bit density of the clock track in bits per inch.

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Clock Track Writing

A two-stage method is utilized to record an accurately closed clock track 11a on a magnetic record disk 11. Two read-write heads 12a and 12b are located over clock track 11a which has a radius r. The heads are spaced from each other along this track by a distance s. The separation s is chosen so that s = 2/m//f, where m is an integer and f is the desired bit density of the clock track in bits per inch.

The first phase of the method requires the production of 2 pi r/s pulses equally spaced around track 11a. In this phase, the leading head 12b is the write station and the trailing head 12a is the read station. Heads 12a and 12b are selectively connected to a write circuit 16 and a read circuit 17 through a read- write control network 18. A bit is first written at a random point on the track by head 12b and the disk is started rotating. Network 18 is such that each time head 12a senses a bit on track 11a, it causes a bit to be written by head 12b. Therefore, when the first bit written passes head 12a, a second bit is written by head 12b. This second bit travels back to head 12a and causes a third bit to be written by head 12b. This operation continues until there are 2 pi r/s equally spaced bits around track 11a.

For the second phase, head 12b becomes the read station and head 12a becomes the write station. The purpose is to multiply the number of bits on the track by two during each revolution of disk 11. In this phase, when a bit passes head 12...