FLEX (protocol): Difference between revisions
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'''FLEX''' is a [[communications protocol]] developed by [[Motorola]] and used in many [[pager]]s. FLEX provides one-way communication only (from the provider to the pager device), but a related protocol called [[ReFLEX]] provides two-way messaging. |
'''FLEX''' is a [[communications protocol]] developed by [[Motorola]] and used in many [[pager]]s. FLEX provides one-way communication only (from the provider to the pager device), but a related protocol called [[ReFLEX]] provides two-way messaging. |
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[[Transmission (telecommunications)|Transmission]] of message data occurs in one of four modes: 1600/2, 3200/2, 3200/4, or 6400/4. All modes use [[Frequency-shift keying|FSK]] [[modulation]]. At 1600/2 this is on a 2 level [[Frequency-shift keying|FSK]] signal transmitted at 1600 bits per second. At 3200/2, this is a 2 level [[Frequency-shift keying|FSK]] signal transmitted at 3200 bits per second. At 3200/4, this is a 4 level [[Frequency-shift keying|FSK]] signal transmitted at 1600 symbols per second. Each 4 level symbol represents two bits for a bit rate of 3200 bits per second. At 6400/ |
[[Transmission (telecommunications)|Transmission]] of message data occurs in one of four modes: 1600/2, 3200/2, 3200/4, or 6400/4. All modes use [[Frequency-shift keying|FSK]] [[modulation]]. At 1600/2 this is on a 2 level [[Frequency-shift keying|FSK]] signal transmitted at 1600 bits per second. At 3200/2, this is a 2 level [[Frequency-shift keying|FSK]] signal transmitted at 3200 bits per second. At 3200/4, this is a 4 level [[Frequency-shift keying|FSK]] signal transmitted at 1600 symbols per second. Each 4 level symbol represents two bits for a bit rate of 3200 bits per second. At 6400/4, this is a 4 level [[Frequency-shift keying|FSK]] signal transmitted at 3200 symbols per second or 6400 bits per second. |
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Data is [[transmitted]] in a set of 128 frames that takes 4 minutes to complete. Each frame contains a sync followed by 10 data blocks. The data blocks contain 256, 512 or 1024 [[bit]]s for 1600, 3200 or 6400 [[bits per second]] respectively. |
Data is [[transmitted]] in a set of 128 frames that takes 4 minutes to complete. Each frame contains a sync followed by 10 data blocks. The data blocks contain 256, 512 or 1024 [[bit]]s for 1600, 3200 or 6400 [[bits per second]] respectively. |
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Revision as of 17:21, 9 May 2008
FLEX is a communications protocol developed by Motorola and used in many pagers. FLEX provides one-way communication only (from the provider to the pager device), but a related protocol called ReFLEX provides two-way messaging.
Transmission of message data occurs in one of four modes: 1600/2, 3200/2, 3200/4, or 6400/4. All modes use FSK modulation. At 1600/2 this is on a 2 level FSK signal transmitted at 1600 bits per second. At 3200/2, this is a 2 level FSK signal transmitted at 3200 bits per second. At 3200/4, this is a 4 level FSK signal transmitted at 1600 symbols per second. Each 4 level symbol represents two bits for a bit rate of 3200 bits per second. At 6400/4, this is a 4 level FSK signal transmitted at 3200 symbols per second or 6400 bits per second.
Data is transmitted in a set of 128 frames that takes 4 minutes to complete. Each frame contains a sync followed by 10 data blocks. The data blocks contain 256, 512 or 1024 bits for 1600, 3200 or 6400 bits per second respectively.
A BCH type ECC is used to improve the integrity of the data. The standard has been designed to allow the pager's receiver to be turned off for a high percentage of the time and therefore save on battery usage.
Since data transmission over FLEX is unencrypted and insecure, transmitting private information over it should be done with caution. There have been reported instances of individuals actively listening to pager traffic (private investigators, news organizations, etc.).