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A radio teleswitch is a device used in the United Kingdom to allow electricity suppliers to switch large numbers of electricity meters between different tariffs, by broadcasting an embedded signal in broadcast radio signals. Radio teleswitches are also used to switch on/off consumer appliances to make use of cheaper baseload tariffs, such as economy 7.
Each of the user companies (the RTS Users, or Service Providers) has its own database on the Central Teleswitch Control Unit (CTCU), which is an HP Integrity computer running OpenVMS on IA-64 for reliability and clustering technology to minimise downtime.
The database defines how each group of teleswitches belonging to the user-company will control the loads and meter registers connected to it. The CTCU uses the database and certain rules to generate and control a continuous string of messages, which is forwarded to the BBC for transmission.
Although each message will be received by all installed teleswitches, the unique user and group-codes carried by the message ensure that only teleswitches carrying the same combination of codes will act on it.
The Radio Teleswitch Service (RTS) has its origins in the energy management projects initiated in the United Kingdom by the Electricity Council in the early 1980s. Three projects investigated the feasibility of using the telephone network, the distribution network and national radio for large scale energy management purposes. The radio teleswitch project was chaired by Walter Waring, deputy chairman of Eastern Electricity, and supported by the BBC.
The idea of phase modulating control and data signals onto the low frequency carrier wave used for broadcasting the BBC Radio 4 programmes was tested. The BBC was satisfied that there was no discernible distortion of its broadcast service and no infringement of its Royal Charter.
The technique won the Queen's Award for Technology, while its application for controlling consumer tariffs and loads was approved by the Home Office. The project was funded by the CEGB and the mainland electricity boards, which were each allocated one of sixteen message channels. One channel was reserved for testing and the final one was allocated to Northern Ireland when it joined the project.
The Central Teleswitch Control Unit (CTCU) system was updated in 2007 to replace the obsolete computing hardware with brand new, modern, fully supported equipment. The old DEC MicroVAX machines were replaced with HP Integrity 2660s. The operating system has also been upgraded to OpenVMS 8.4. No effort has been made to upgrade the obsolete transmitter hardware.
All communications lines have also been updated and Internet access has been introduced in addition to the dial-in access by modem.
The update has markedly improved the performance and stability of the system.
The new system went live at the end of January 2008.
For convenient and practical operation of the system the users needed to set up or appoint an organisation to take overall responsibility for managing the delivery of the service. The organisation needs to hold nominal ownership of the system and IPR and as an agent to enter into and manage contracts necessary for the delivery of the service. The managing agent also provides co-ordination and liaison roles between all the parties concerned.
The Electricity Association (EA), which was previously known as the Electricity Council, entered into a renewed formal agreement with the BBC in 1996 as an agent of the users. The EA had also negotiated an agreement with the National Grid Company (NGC) concerning the servicing of the CTCU. Since 2004 the functions of EA regarding this contract have been taken over by the Energy Networks Association.
The Radio Teleswitch Service is broadcast alongside the longwave output of BBC Radio 4 from the Droitwich Transmitting Station. This transmitter uses a pair of obsolete metre-long valves which are no longer manufactured anywhere in the world.
In October 2011, the BBC admitted that the Droitwich transmitter, including Radio 4's longwave service and Radio Teleswitch, will cease to operate when one of the last two valves breaks, and no effort would be made to manufacture more nor to install a replacement longwave transmitter.
The BBC stated that their plan is simply to cease broadcasting on longwave forever once the Droitwich transmitter fails. It has been reported that the BBC estimated that less than ten spare compatible valves existed in the world, and that each valve had a working life of between one and ten years. However, ex-BBC engineers say the valves are ceramic, not glass and these valves can be made to order, perfectly safely.
A 50 kW longwave transmitter transmitting a 1000 Hz wide signal could take over the teleswitch role with adequate nationwide coverage—but some legal provision would probably have to be made to make this possible.
References and more information
- Adapted from: "An introduction to the Radio Teleswitch Service". Shau Sumar - EA internal document, 2003.
- D.T. Wright: L.F. radio-data: specification of BBC phase-modulated transmissions on long-waves, Report1984-19, BBC Research & Development, January 1984
- British Standards: BS 7647:1993 "Radio teleswitches for tariff and load control"
- Energy Networks Association