Radio signal broadcasts have their usefulness, but they eventually end (except, perhaps, for SETI). Every so often, we mark the public end of a once-essential wavelength, such as 3G cellular, analog television, or the Canadian time check. One of the most weirdly useful signals will soon end in the United Kingdom, with notable consequences if its transition is not properly handled.
Beginning in the early 1980s, UK homes could have electrical meters installed with a radio teleswitch attached. These switches listened for a 198 kHz signal from the BBC's Radio 4 Long Wave service, primarily broadcast from the powerful Droitwich Transmitting Station. These switches listened to 30 messages per minute, waiting for a certain 50-bit data packet to arrive that signaled that electricity was now at cheaper, off-peak rates ("tariffs" in the UK).
With this over-the-air notice, homes that bought into Economy 7 or Economy 10 (7 or 10 hours of reduced-price power) could make use of ceramic-stuffed storage heaters that stayed warm into the day, prepare hot water heaters, and otherwise make use of off-peak power. How the electrical companies, BBC, and meters worked together is fascinating in its own right and documented in a recent video by Ringway Manchester (which we first saw at Hackaday).
© Richard Harvey (Public domain)
