Popular Mechanics - Plus ca change

Couldn't find that, but twin filament lamps (giving 3 power outputs) are common in the US, so common that CFL versions of them are made too. They use an ES base with an extra ring contact.

So it opens up at the end with an advert for Camel cigarettes...

"Why did you change to Camels, Dennis O'Keefe?" "My cigarette must be kind to my throat and Camels agree with my throat - pack after pack!"

Wikipedia: "A heavy cigarette smoker, O'Keefe died of lung cancer in 1968 at the age of sixty."

Not much option in '52, as practical household dimmers were many years away. It would also depend on the price - and of course would require special wiring. And if the lamp is expensive, when one filament fails...

FWIW, I'm not convinced that dimming a halogen does cause it any harm. I've been doing it for ages here and haven't seen any evidence. TV studio lamps were also halogen and dimmed - although not usually as low as you'd do at home.

Dim-dip headlights, back in the late '80s, early '90s - the dip beam (Halogen was ubiquitous at the time) was run at about 10% if parking lights and ignition were both on.

"Received wisdom" is that it does murder bulb life, but the vibration of running in a car at the same time may play a part in that.

Tend to agree at the "slightly dimmed" end of the scale. And at the "very dimmed" end, well, it is probably not hot enough to make much difference. There is probably a patch somewhere between the two where it does have a significant effect.

Maybe it was that? Unfamiliar as I am with them, I simply assumed triple. But 50 + 100 would make sense and be fewer filaments...

Dim-dip came in well before halogen headlamps.

For halogen lampsthe theory was that because the lamp ran cold, the inside would blacken much quicker, thus reducing lamp life. [For those supporters of thn "dark sucker" theory, they filled up quicker].

Were these part of the "Camm's Comics" range? No I guess that would be "Practical Mechanics" If there was such a beast. I was an avid reader of Practical Radio then later Practical TV. Those were the days.

Not many vehicles tended to be fitted with those, except London black cabs

- and they seemed to used the old Lucas sealed beam units long after most had gone to halogen.

I thought it was meant to cause blackening of the envelope rather than total failure?

I have old downlighters in the kitchen lighting some of the work surfaces. Originally plain RO80 tungsten - now PAR type halogen. They are frequently dimmed. No signs of blackening, and without any doubt last much longer than the originals. As well as looking better. Just as well at the price. ;-)

Practical Wireless, surely?

The Dim-dip I'm thinking of was a UK-only, very short lived idea required to be fitted to all new cars for a few years first registered after

Halogens were well on their way to ubiquity a decade before that.

In 1988, the European Commission successfully prosecuted the UK government in the European Court of Justice, arguing that the UK requirement for dim-dip was illegal under EC directives prohibiting member states from enacting vehicle lighting requirements not contained in pan-European EC directives. As a result, the UK requirement for dim-dip was quashed.[20] Nevertheless, dim-dip systems remain permitted, and while such systems are not presently as common as they once were, dim-dip functionality was fitted on many new cars well into the

Wiki

The first halogens seem to have been launched around 1959.

Must have been very short lived - I has an F reg BMW without it.

or the Black Man's Wheels is a dodgy import....

Jim K

Slightly, will increase lamp life usually. Too much however will stop the halogen cycle and lead to blackening and reduce life as a result (the blackening being the filament in vapour form spread all over the glass)

We had lamps like that in the 1970s (USA). The problem is that with three filaments in one lamp, the lifetime is shorter before one of them blows.

And I have an early E-plate Mazda without it. But it may have got through on ECE48 type approval instead.

Theo

They were compulsory on all new cars in the UK, except those fitted with suitable separate lights - which just about only meant Saab & Volvo, with their 21w DRLs.

Even Citroen bothered to fit it to 2cvs - despite not bothering with other legal requirements like a main beam warning light (which is causing all sorts of MOT fun'n'games, now that that's become testable...)

Our '90 205 has it, but only because I've not yet found out where the bits are to rip 'em out!