This device was used to switch on various heating and hot water loads at night, and at the same time change the rate on the electricity meter so that a lower price would be charged.
Orignally intended for Economy 7 and similar tariffs, this would switch on storage heaters and hot water heaters overnight, typically for a 7 hour period somewhere between 11pm and 7am.
Switching commands can be transmitted in real time, or alternatively only updates transmitted to configure the internal clock and timer.
Although most typically used for overnight heating, the system can be switched at any time, and could theoretically be used to disconnect heating loads in the event of a sudden shortage of electricity generation, or for various other purposes.
In this video, the teleswitch is dismantled and the insides examined.
As of 2018, these devices still work, receiving radio signals on 198kHz from a transmitter at Droitwich. The example in the video is a separate device, although electricity meters exist which have the teleswitch functionality built in.
The future of this service is unclear - it is likely that smart meters will replace it, however no timescale is available for this.
This example still works, and in this video is shown operating. It has two switched outputs rated 25 amps and 80 amps, for hot water and heating respectively.
Two other outputs would be used to change to different registers on the electricity meter to allow different prices to be charged for the different types of load.
In this timelapse video, all of the outputs are connected to neon indicators to show when the various outputs are energised.