Difference between revisions of "Frequency Modulation"
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'''Frequency Modulation''' (or '''FM''') is an encoding technique, used in [[magnetic storage]] such as [[disk]]s and [[Disk#Low-cost disks|floppy drive]]s. | '''Frequency Modulation''' (or '''FM''') is an encoding technique, used in [[magnetic storage]] such as [[disk]]s and [[Disk#Low-cost disks|floppy drive]]s. | ||
| − | In FM there is a reversal (signal level, or magnetic flux) at the start of every data bit time; for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'. | + | In FM there is a reversal (signal level, or magnetic flux) at the start of every data bit time (i.e. every clock time); for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'. |
Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name). | Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name). | ||
Revision as of 16:34, 25 October 2017
Frequency Modulation (or FM) is an encoding technique, used in magnetic storage such as disks and floppy drives.
In FM there is a reversal (signal level, or magnetic flux) at the start of every data bit time (i.e. every clock time); for a '1', there is an additional reversal in the middle of the bit time, with no reversal indicating a '0'.
Consecutive zeros show a reversal between data bit times; consecutive ones show two reversals in every bit time (i.e. doubling the frequency of reversals; hence the name).
It was mostly replaced by Modified Frequency Modulation, which can store twice as many bits in the same maximum reversal rate.
