The writing is on the wall for the Radio TeleSwitch service that may still be turning your heating and hot water on and off. If the latest deadline is to be believed, and it has come and gone many a time over the preceding decade, then the radio teleswitch service will be no more after 30th of June. But what does that even mean and why might it leave you or yours in hot water?

Or… cold water, because if you still have a radio teleswitch as part of your electrical installation, duly dictating just when your hot water and/or space heating operates, then from the beginning of July it may be a dead lump on the wall that does precisely bugger all, so let’s take a peek at what these things are, why anyone even has them, and how the bastions of the BBC have been the ones keeping your heating appliances clocking on for perhaps the past forty years!

Back in the 1970’s, the grid struggled with the demand of everyone getting home from a hard day’s activity of industrial action, standing before a blazing brazier listening to an inevitably northern union loudmouth with short-man syndrome, outside of the factory they were supposed to be pulling their weight in, and putting on the heating and hot water. Therefore, a way to shed… or spread the load was needed.

The first solution was the analogue mechanical timeswitch. This would be set to turn on its output in the dead of night when demand was low and it could be used to heat a tank of water ready for the morning, or to charge storage heaters in preparation for the next day.

TimeswitchAn old-skool timeclock before the RTS became commonplace


Our timeswitch would itself often be connected to a secondary fusebox that would usually be wholly unpowered during the day, then would clock on at night as the timeswitch commanded. There may be several fuseways and circuits from such an off-peak consumer unit duly serving multiple heaters as well as the hot water tank. The trouble with timeswitches is accuracy: once an electromechanical clock has been set, how can you ensure its kept in check? After all, all timing devices suffer from drift.

Take any two standalone clocks or wristwatches – analogue or digital, and set them identically against GMT. Other time zones do exist, but as a subject of His Majesty, one rightly refuses to recognise them of course. Once we have “synchronised watches”, as they used to say in war films, then even if you have two timepieces from off the same production line, tiny mechanical losses or variations in electronic component tolerances will mean that, given days or weeks, they’ll start to drift apart both from the time zone we originally set them to and from each other. For cheap timepieces, that’s not really an issue, after all, who cares if your wristwatch starts to move a few seconds or even minutes from true over several months so long as you know roughly when happy hour starts down at the local?

If connected to the mains, a more modern timeclock could use the 50Hz frequency, or 60Hz in some countries, to count the cycles of the incoming supply, fifty of which would equate to 0.02 seconds, allowing time to be kept quite reasonably. It will still drift a little eventually because the mains frequency will itself jitter within certain tolerances, and in the event of a power cut, such a clock would fall back to its own battery backed-up internal oscillator, whose accuracy may not be very good, until it can start counting incoming sine waves again.

Old school timeclocks would have been very well engineered and highly accurate once set, and would incorporate a mechanical movement to keep it ticking through a power cut. Nonetheless, this pensionable product would lose precision over a prolonged period, so the boffins sought something more accurate. And in the early 1980’s, by Jove, they had it in the form of the Radio TeleSwitch or “RTS”.

And pictured here is one of the friggin’ things:

Teleswitch


This is a 1990 model removed from a defunct electrical installation, and is part of the network equipment belonging to the grid. Other flavours existed throughout the years including the Telemeter, a hybrid of meter and teleswitch, but the keywords to look for are “Radio Teleswitch” written on the thing. It’s this device that may be turning on your heating and hot water in the dead of night.

Back in the 1980’s, the boffins figured they could use the Radio4 LongWave broadcast on 198kHz from a massive transmitter near Droitwich and two subsidiaries in Scotland at Burghead and Westerglen to encode timing and control signalling by phase modulating the carrier wave. It’s these signals that our trusty teleswitch is listening out for on its AM antenna buried within.

I’ve had my example teleswitch hanging around for some years now, so at the time of writing in the wintery depths of January 2025, I decided to power it up to see if it still operated… and it does. Now, at my advanced age, I like to be tucked up in bed with a warm wife, a purring cat, and randomly malfunctioning dick-spring at a reasonable hour of the late evening, so I’m not hanging around all night to see what this up to. Therefore, to test it, I connected a Chauvin Arnoux PEL-51 logger to watch over what it was doing and when...


Trace

Looking at the data capture, we see that magically, just after midnight, my teleswitch clicked into operation having received and decoded the relevant signal from Droitwich. The PEL51 trace shows switch-on occurred two minutes past pumpkin o’clock and the output remained live until 07:03. There were no further events over the monitoring period with the PEL51 running for about a day and a half, so this teleswitch is configured for the Economy 7 tariff. Economy 7 was introduced in the 1970s to provide seven hours of cheap off-peak electricity overnight for the purposes of water and storage heating. Other tariffs were available such as Economy 10 which provided an additional three hours of low-cost power, hopefully in the late afternoon, to give your heating appliances a boost for the oncoming evening.


Economy 7 is still a valid tariff today, and I myself was using it until relatively recently even though my humble abode never had a teleswitch. What I did have was an EV and a storage heater in my hallway, so cheap electricity at night came in handy, however for me Economy 7 was just a tariff with no physical switching involved. Instead, switching was local, that is to say, the storage heater and EV each knew the time of day themselves and when to power on, and my digital two-rate meter clicked over from peak to off-peak for seven hours each night without needing a signal, presumably based on its own internal quartz clock, although Christ knows how accurately that was set.

Although Economy 7 is billed as providing seven hours of cheap power at night, what that really means for those running without a teleswitch or smart meter is “seven hours at some stage during any 24-hour period” and it depends what’s telling your meter to click over to night rate and when. If you’re relying on an old timeswitch, it might be out of wallop enough to be clicking over in the middle of the day which may work out to your advantage… or not.

Today, there’s no such thing as cheap electricity and those paying a lower rate on Economy 7 will get bum-fisted on their peak charges which makes it non-viable unless you’re really drinking the juice in the small hours. Once I’d sacked off my EV, that was no longer the case for me, so I binned off the storage heater and moved back to a flat-rate tariff.

The BBC, when not undertaking sneaky tricks to extort a television tax out of the population, hiding its paedophile past or giving high-paying jobs and industry breaks to the offspring of juiced-in has-beens have been murmuring about shutting down Droitwich for over a decade now. They apparently say the Droitwich transmitter is operating on two valves for which spares are few, if any, although word on the street indicate that’s perhaps not the case. Nonetheless, a transmitter this powerful must cost a packet to run and so the Beeb is pulling the plug on Radio4 longwave at the end of March 2025 so they can (probably) splurge the money on “the right people” instead. As for the RTS signalling, at present that’s due to be switched off on 30th June which means your teleswitch will no longer receive any instructions as to when it should punch in and out of its nightshift. So, let’s explore the options open to those who still have them.

Option 1: The last signal transmitted is to turn teleswitches off.
This seems unlikely as it would leave any dependent off-peak CU and related heating appliances all quite inoperable. I don’t advise it, but you could cut any supplier seal on the teleswitch, remove the front cover and manually switch the damn thing into the ON position to power their off-peak gear, but that would be interfering with network equipment belonging to the distributor and it would expose you to live parts. Also, on the next meter read, you may find yourself prosecuted for what would amount to meter tampering even though you’re just trying to keep the radiators running to dry out your pants and socks.

Option 2: The last signal sent is to turn teleswitches on.
This might make more sense as it would leave your heating and hot water working, although without the automated control, you would need to ensure your storage heaters and hot water tanks are all individually, manually operated. These appliances usually have their own localised isolators, so this option makes the most sense as nobody would be left in the cold. When it comes to billing after the shut-off date, energy companies will continue to collect Rate 1 and Rate 2 readings from customers and, presumably, apply a flat-rate to the billing regardless. If you want the benefits of a flexible tariff such as Economy 7, then the energy providers will have to know they can control the rate switching, which brings me onto option 3.

Option 3: Have a smart meter installed.
Smart meters are a garbage product badly done, but they’re the only way to replace the functionality of a standard meter plus teleswitch. If you want to retain the automatic switching at a consumer unit level to take advantage of a two-rate tariff, then a smart meter is the best option because her energy company will install it at no charge. One tip is to insist on them also installing an external isolator for free which many providers will agree to in order to get a smart meter on your wall. A massive annoyance with smart meters is that the in-home display, the fucking dingus-widget they sell the thing on so that you can monitor your usage and budget for it, will fail within a few short months or years and none of the energy providers seem to want to supply you with a new one when that happens, leaving you clueless about your daily energy spend…

..although, I must admit, since my own in-home display died recently, my anxiety over my daily spend has relaxed like an octopus’ inkhole. When it did work, I’d worry about the pounds and pence ramping up, all of which I had no control over as it was just basic heating, cooking and living in my electric-only home in which I’d already pulled the plug on any ancillaries. Now that I can’t see my beer tokens disappearing in real time on my “energy shaming device”, I find I give fewer fucks about it.

IHD


The government waded in within the last year to try and force energy suppliers to change out faulty IHDs citing evidence that an increasing number of consumers require replacements but are not always able to get them. Apparently, the behemoth energy providers have all begrudgingly agreed to adopt this, so good luck getting past some pest in their customer services when your in-home display fails.

Option 4: Lose the off-peak altogether.
Let’s say you don’t want a smart meter and insist on keeping what you have, but the teleswitch is defunct. We don’t need to tamper with network equipment – that wire from the teleswitch which feeds your off-peak consumer unit is your property, not the networks. We could chop that son of a bitch and re-route so that your off-peak consumer unit is now also powered 24/7, however, you would need to operate individual appliances manually through their isolators or install localised timers to automate operation. We could also choose to run your off-peak CU from a spare way in the peak board or from an external timer and contactor of our own to keep things clicking in and out overnight as before, but again, your supplier will likely bill you at a flat rate because they no longer have control over when a cheaper tariff is to be applied, and your existing meter isn’t likely clever enough to switch between rates without instruction from the network.

The energy regulator Ofgem apparently has a task force, which sounds cool and dynamic, set up to inform affected customers by the end of 2024 that their RTS is to become obsolete and for them to arrange with their provider to get a smart meter, but some of my clients are only just getting word now mere months before the switch off is scheduled. In some cases, an RTS isn’t even installed, yet the supplier is still putting the willies up people by saying they’ll lose heating and hot water unless they get a smart meter. The truth is the suppliers don’t know what’s installed out there, so they just play it safe by worrying anyone without a smart meter with the threat of service being lost.

Eon


Even if you have a teleswitch it may be long defunct. Look at how many wires are going into it – if there are just two or three wires on the left side, then that generally means it’s powered but not doing anything. There are many timers and teleswitches out there that have long since been relieved of duty but remain physically present and ticking over. Below is an example of one that's present yet doing zip-all.

RTSoutofuse


I believe an RTS has its own internal clock, reset from the Droitwich signal every day, and will keep on operating based on that clock even if it doesn't get any radio updates. It will drift over time, but ought to carry on working despite dire warnings from your energy supplier. The Radio Teleswitch was an interesting and effective means to an end and I doff my McHat to the eggheads who came up with the concept. It served us well for over forty years; however, progress seemingly marches ever backwards these days and now we have the all-inferior smart meter taking over from the working and well-engineered hardware of yesteryear.

Other countries figured out a better way of signalling through modifying the AC mains waveform but trust us bloody Brits just have to do it differently!

 
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