FLEX is a
communications protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchr ...
developed by
Motorola
Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorol ...
and used in many
pager
A pager (also known as a beeper or bleeper) is a wireless telecommunications device that receives and displays alphanumeric or voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknow ...
s. FLEX provides one-way communication only (from the provider to the pager device), but a related protocol called
ReFLEX provides two-way messaging.
Protocol
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 11 data blocks. The data blocks contain 256, 512 or 1024
bit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...
s for 1600, 3200 or 6400
bits per second respectively.
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
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
usage.
Security
Transmitted data over FLEX is not encrypted. A
BCH error correcting code
In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is ...
is used to improve the integrity of the data, although this is not cryptographically secure.
There have been reported instances of individuals actively listening to pager traffic (private investigators, news organizations, etc.).
Usage
In
The Netherlands
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the emergency services use the Flex-protocol in the nationwide
P2000 network for pagers. The traffic on this network can be monitored online.
In
South Australia
South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
the State's SAGRN network for the Emergency Services paging system (CFS, SES, MFS and SAAS) is run on the FLEX 1600 protocol, and can be monitored online.
See also
*
ReFLEX
*
Mobitex
Mobitex is an OSI based open standard, national public access wireless packet-switched data network. Mobitex puts great emphasis on safety and reliability with its use by military, police, firefighters and ambulance services. It was developed in t ...
*
DataTAC
External links
FLEX: The New Edge For The Paging IndustryDesign And Implementation Of A Practical FLEX Paging DecoderUS6396411B1: Reliable and fast frame synchronization scheme for flex paging protocol
References
{{Motorola
Network protocols
Motorola
Radio paging