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
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
provides two-way messaging.
Protocol
Transmission
Transmission may refer to:
Medicine, science and technology
* Power transmission
** Electric power transmission
** Propulsion transmission, technology allowing controlled application of power
*** Automatic transmission
*** Manual transmission
*** ...
of message data occurs in one of four modes: 1600/2, 3200/2, 3200/4, or 6400/4. All modes use
FSK modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...
. 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 represented a ...
s for 1600, 3200 or 6400
bits per second
In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time.
The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction w ...
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 usage.
Security
Transmitted data over FLEX is not encrypted. A
BCH error correcting code 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 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 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
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
*
Mobitex
*
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