Operation London Bridge: the death of the Queen

Yes - Radio 4 LW has a data stream used for a number of low bitrate systems. Didn't know RATS was one of them. AIUI the BBC said they were considering discontinuing BBC R4 LW if the transmitter failed, as repair/replacement wasn't deemed economically viable. Wonder how many of the systems hanging off the data feed have a plan B? (It is, or certainly was, used to trigger electricity metering between high and low tariff 'Economy 7' ISTR)

I believe the rush to get everybody onto a smart meter may be your answer to that one!

It's not just the E7 stuff that is carried by R4 LW, I'm told some government agencies also use remote signalling facilities on there.

I can confirm this is correct - whilst London Bridge is used to a degree in the way the Guardian article talks about, for overall planning and preparation (events, people, equipment etc) and then - presumably - for operation, its known as [REDACTED].

Are there any websites with analysis of the signal or anything useful/interesting to read about it?

There is something in one of the old BBC engineering monographs I think, but it doesn't specifically mention RATS.

Doesn't seem like a good one, I've read lots of articles about code words over the years and they all use REDACTED too!

There is a BBC R&D paper from the 80s that defines the signalling code - but not the usage of the data. It essentially allows small packets of data to be sent to specific groups - how that data is then used and defined is up to those groups I imagine.

Article from the Guardian about this, itself now 5 years old(!): https://www.theguardian.com/media/2011/oct/09/bbc-radio4-long-wave-goodbye

RATS is a pretty closed system, so could be accommodated by other means as part of a refresh. Perhaps RATS alarm signalling could switch to BBC Satback, and be backed-up within DTT? If not then the BBC's WAN ought to be robust enough, with even the possibility of reasonably well-coded messages sent across the public internet.

The Economy 7 signalling is made redundant by smart metering, so the electricity industry ceases to be a customer.

Given that the broadcast value of 198KHz, according to the BBC is dwindling; then the only real value of the thing is national resilience. Droitwich (ignoring Burghead and Westerglen for the mo) is as the only tx that can talk to the entire country. The value is of course that if you wanted to talk to a battered and distressed nation, rx battery life is a factor. The Cabinet Ofice (haven't got the reference) have produced a paper discussing the relevant scenarios of battery life in the domestic receiver population, considering FM and even DAB. Long Wave is a feature that has been designed out of most households' requirements, so the population of sets is probably dwindling along with Radio4 LW's audience.

If there is a requirement for a LW broadcast to be receivable across the UK after a cataclysmic event, then perhaps a cheap form of mass-produced emergency radios needs to be produced. The receivers (wind-up?) could even adopt features such as remote awake from standby, or selective calling. However, to be of any use, there needs to be a level of resilience that assumed more that one tx site, EMP protection and some level of messaging security.

I see that the Imperial War Museum have re-printed Protect and Survive .

The use of LW in a national emergency has been long superseded I believe. As you say the number of LW receivers is very low in this day and age.

Last year someone did an FOI request for the 1977 BBC War Book. This is the full instructions of how the emergency broadcasts will work and included scripts. I was quite surprised that even back then LW wasn't a major part of the plans, in fact IIRC it was to be closed down. This was because the plan then was for regional broadcasts from underground facilities around the country using FM and MW.

As for RATS, the beauty of using a radio system is that the receiver can be anywhere. Using a satellite based system or even an Internet based solution wouldn't be as flexible and the latter far less reliable

And part of that plan was for certain underground facilities to have RATS receivers....