A radio teleswitch is a device used in the United Kingdom primarily to allow electricity suppliers to switch large numbers of electricity meters between different tariff rates, 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 differential tariffs such as Economy 7. As a consequence of the final end of radio transmissions on 198 kHz long wave, the UK-wide teleswitch service permanently ceased on 30 June 2026.
Service role The typical use of a teleswitch is to manage the start and end times of off-peak charging periods associated with tariffs such as Economy 7 and Economy 10. This includes switching between 'peak' and 'off-peak' meter registers as well as controlling the supply to dedicated off-peak loads such as night storage heating. The use of dynamic switching instead of a fixed timer allows some additional demand management, such as by flexing start and finish times for electric heating loads according to prevailing overall demand levels. Some suppliers also offer more sophisticated heating control using the radio teleswitch network. For example, Scottish Power 'Weathercall' and SSE's 'Total Heat Total Control' both dynamically vary the length of time storage heating is energised each night depending on the forecast temperature for the following day to help maintain a consistent household temperature. Teleswitching has also been used to help level out demand in areas where the supply network is close to capacity. In the 1990s, Manweb used such a system to provide different households with different off-peak periods on a weekly alternating basis. By spreading out the high peak demand associated with electric storage heating in Mid Wales, the company avoided upgrading costs of over a million pounds, and £200,000 a year in reduced use-of-system charges. In the north of Scotland, the radio teleswitch service is also used to help control the local electricity distribution network for resilience purposes.
Operation 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 HPE 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.
History 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 new system went live at the end of January 2008 and the update has markedly improved the performance and stability of the system. In 2016, it was reported that over 1.6 million teleswitches were in use. Around 190,000 were reported as being used dynamically to control loads such as heating on a day-to-day basis, with the remainder following generally fixed switching times that were updated less frequently. In early 2020, 1.4 million electricity meter 'MPAN' locations were thought to still be using radio teleswitching – although the actual number of individual premises may have been lower as some single-household installations use two MPAN references for historical technical reasons. By the end of May 2025, the number of radio teleswitch meters left in service had reduced to 314,395.
Formal agreements 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.
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