The system basically comprises user terminals
and modems, the central teleswitch control unit (CTCU) the LF Data
System, the 198 kHz BBC Radio Four transmission system and radio
teleswitching receiver controllers (RCs).
- Each user of the system, the Distribution
Networks Operators (DNOs) and Transmission Network operator (TNO)
has a unique set of codes enabling them to address only their
own block of meters and switches.
- These instructions are sent by the DNOs to
the Central Teleswitch Control Unit (CTCU) housed and maintained
by Cygnet Solutions.
- The CTCU processes and forwards their switching
codes to the BBC Message Assembler at Crystal Palace.
Here, the electricity industry codes are combined
with the instructions from other users of the service and sent to
the three national networks of transmitters. The main transmitter
also the BBC site), rated at 500kW, can reach most parts of
the UK and some parts of continental Europe while the two smaller
transmitters located at Westerglen
cover Scotland and Northern Ireland.
At present, it is understood that the only other
user of the system is the Environment Agency who use the system
to disseminate flood warnings. Messages are encoded onto the Amplitude
Modulated (AM) Radio 4 signal using Phase Shift Keying (PSK) techniques.
30 messages are transmitted per minute, each
message having 50 bits of data. 18 of these bits are taken up by
a BBC header and Cyclic Redundancy Check (CRC) tail. 32 bits are
available for data.
The RadioTeleswitch specification (BS7647) lays
down specific formats for its user message contents. Two message
types are defined:
- command (or immediate) which has priority
of broadcast, and on receipt immediately sets a Teleswitch (RCs)
internal switches to required status, overriding any programmed
- programme, which updates or refreshes the
operating program stored within a Teleswitch (i.e. internal switches
will not change status until required by the program).
An 'immediate' instruction can take one or two
minutes from initiation of a request at the terminal of a user,
depending on other traffic on the data system, and is intended to
allow fast, broadcast load shedding.
The system's ability to offer users both programmed
and immediate broadcast control have enabled companies using the
system to provide weather-related control of electricity storage
heaters in specialised arrangements such as 'budget warmth' and
'heat with rent' schemes.
The transmission of cost reflective messages
and weather forecast information has allowed the concept of controlled
consumption to be extended to provide more comprehensive forms of
premium heating and other services. The ability to influence demand
patterns more finely so that they respond more immediately to changes
in supply cost, is to the advantage of both suppliers and customers.
It gives customers another form of choice.
Other applications already in place, or currently
possible, include regional flood warning alarm systems, common remote
control at multiple sites, such as weather-related environmental
control in unmanned buildings, the control of services such as water
and gas at point of entry into premises or, in the case of water,
at points of connection to storage tanks and the replacement of
other more expensive in-house remote control systems (see
If a simple, readily-available, economic, one
way data communication channel is a requirement then Radio Teleswitching
can meet it in a very short time.