[Bennyboy84]

After watching some 80s closedown clips on YouTube this is on quite a few of them.

I'm sure this has been asked before but why did they used to do this?

[Neil Jones]

After watching some 80s closedown clips on YouTube this is on quite a few of them.

I'm sure this has been asked before but why did they used to do this?

Potential fire hazard. Simple as.
Remember TVs of old didn't have auto power off after not receiving a signal/seeing snow for five minutes, but by the time TVs came along that could turn off after five minutes of snow, television services were available 24hrs.

That being said, any electrical item is a potential fire hazard either faulty (or going faulty) or is used inappropriately enough.

[James2001]

Didn't valve driven TVs get quite hot as well? There would still have been a fair number of them around in the 80s.

[Blubatt]

Didn't valve driven TVs get quite hot as well? There would still have been a fair number of them around in the 80s.

405 Line signals only went off in 1984, so very likely yes.

[Moz]

Didn't valve driven TVs get quite hot as well? There would still have been a fair number of them around in the 80s.

They did. I can remember putting my hand over the back when I was a kid and it was too hot to hold it there for more than a second.

[James2001]

Didn't valve driven TVs get quite hot as well? There would still have been a fair number of them around in the 80s.

405 Line signals only went off in 1984, so very likely yes.

There were 625 line and colour valve sets as well.

[Steve in Pudsey]

I think there was something about a set that wasn't receiving a signal being more prone to overheating or something like that.

Why did these courtesy announcements only go out on ITV and not usually the BBC? (Some of the regional closedowns do include it) Was it less of an issue with a set tuned to Band I vs Band III?

[Larry the Loafer]

Didn't the tone also serve as an audible wake-up call (not it's only purpose, I'm presuming) for anyone who might've fallen asleep in front of the box, or for anyone who thought their black screen meant their set was already off?

[Bluecortina]

Didn't the tone also serve as an audible wake-up call (not it's only purpose, I'm presuming) for anyone who might've fallen asleep in front of the box, or for anyone who thought their black screen meant their set was already off?

IBA transmitters had ‘silence’ detectors - if they detected no audio for a period (2 minutes from memory) they would automatically transmit a locally generated apology caption. So to prevent this, as the transmission staff were putting on their hats and coats before leaving the building they would output black/bars/test card and tone to the transmitter as they rushed out to their cars.

[Clean Feed]

Didn't the tone also serve as an audible wake-up call (not it's only purpose, I'm presuming) for anyone who might've fallen asleep in front of the box, or for anyone who thought their black screen meant their set was already off?

IBA transmitters had ‘silence’ detectors - if they detected no audio for a period (2 minutes from memory) they would automatically transmit a locally generated apology caption. So to prevent this, as the transmission staff were putting on their hats and coats before leaving the building they would output black/bars/test card and tone to the transmitter as they rushed out to their cars.

This example from late-1981 shows the blue caption kicking in less than 30 seconds after loss of video.

www.youtube.com