I wonder if a reason for two bulbs per side is redundancy, making it immediately obvious if it's a dead bulb or other fault

Thanks for showing this to us, I had no idea. The awesomeness of the Apollo program is palpable even in this lowly ground control switch! And now I know I NEED one...

I was quite impressed that Fran just happened to have the bulbs lying around. :-)

I’m surprised you didn’t have the switches hooked up to toggle the lamps with each push (and some litho inserts) to say [green] FRAN [red] LAB, FRAN, LAB, FRAN, LAB…

Back in the 70s I worked on control panels using these type of switches. They were difficult to fix when broken. This usually happened when the switch was worn from many cycles. Nice memories.

_"I'm going to have to hook this up"_ If anyone wasn't expecting this then shame on you 😁

At work we had a big box of similar modular switch assemblies that were salvaged from some old vacuum gear, that we used in all sorts of internal prototypes and lash-ups. We never bothered to remove the old decals so the buttons and lamps never said what they actually did. Our favourites were the buttons that were simply labelled "Baffle".

I owe you an apology in that when I saw a during of 20 minutes I thought that is pretty long for just an illuminated switch, but in fact I found the entire video riveting. Thanks for posting it.

I share your interest in illuminated indicators. I was a military avionics tech in the late 1960s, aircraft cockpits tend to be full of these types of indicators.

Neat how the plastic rotor in there could be notched out to make it into a customizable sequential switch.

Having seen these in use, what they did for dead bulb detection was use a ?47 ohm 2W resistor to feed the lamp in the "off" condition, so that it would have a slight glow. No glow = lamp open

My company used tons of those "back in the day" and they were VERY expensive. And since we were not not smart enough to run the bulbs at a slightly reduced voltage, they ate bulbs at a high rate. Bulbs were expensive and Master Specialties never made it easy to remove the lenses. It's jewelery and costs like jewelery.

It's the tiniest thing but I have to appreciate that this seems to easily be maintainable while it's not only installed but also powered. The common making contact before anything else is the main thing that suggests as much to me, one of those "someone really cared" sort of details. I love switches. It sounds silly when I say it out loud but it's true.

Marvelous stuff Fran! My studio at the Beeb had a similar switch, though from a different manufacturer. Being modular you could have the same front end indicator with different switches, so some were not latching, and you could also make them change over. The ones we had didn't have that clever rotating action. We had a special pair of tongs to get the bulb assembly out. The front slid off, then you could get the tongs down the sides to unlatch the assembly and pull it out. The bulbs had the same coloured caps, and the legend was on a piece of transparent celluloid, done with Letraset. The bulbs were 27V but run at 24V, and we even had special tongs for pulling them out! The great thing about them being modular was you could make pretty much any sort of switch you wanted. Their main use in the studio was to operate the internal video routing. The push buttons worked a big relay matrix, which in turn operated video and audio switching. It could be a nightmare to troubleshoot. The latching mechanisms were so clever. Those rollers could be different shapes so you could have 1 or 2 micro switches NO and the other NC. And since they were operating realays in the racks in another room, the lights were switched separately. Lots of long runs of multi core wiring.

I love how mechanically over engineered everything from the slide rule era is!!! I bet that thing would last 100 million cycles. (Edit, I am being hyperbolic with the 9 figure cycle count, but I would bet that thing outlasted any system it was used in)

Look for one with the label "DESTRUCT" That would be pure gold.

This is a blast from the past for me. In the early 80s I was working in the UK at a USAF satellite communications station at RAF Croughton and the AN/FSC-78 master control panel used those switches for status and control of the transmitters and some ancillary functions. The control panel interfaced to the station hardware through a control box (3'x3'x4' lwh) that was 54 series TTL.

What a fun video! I realize how pretty your hands are, and I wish my hands were that pretty! I guess it’s all those years of operating machine equipment have taken their toll on my little bunny paws... I have always loved the light up switches on machines, the very first electrical anything I played with as a kid we were lightbulbs, so I thoroughly enjoyed watching this video!

As an instrumentation engineer in the 1970s, I used to specify those switches. Used them for a control panel at the IBM Poughkeepsie physical plant. Also spec'd them for use in jet engine test cells/hush houses at Naval Air Rework Facilities and Top Gun near El Toro. They were more expensive than competitive switches by (say) Square D. But they were also more customizable.

silicone colored bulb caps are very common in car instrument clusters before led's were widely used. My car is full of them.

I've worked with a lot of milspec and aerospace kit. They're all beautifully engineered like this :)

Nicely done. Thanks for taking the time to share the joy of this gem. There aren't enough beautiful tactile or mechanical switches left in the world. I'm actually in the process of having to design a new bezel from spun up acrylic unfortunately as no light pipe makers do anything even remotely nice over about 5mm these days.

Fran, you are AMAZING!! I just discovered your channel and you have already blown our minds with your incredible videos about the Apollo launch vehicle ejectable film canisters, the F1 engine design, and the brain-bending design of the Mission Control video displays, and right now we are watching your exploration of the Mission Control panel switches. You have made my day!! What a terrific communicator you are!!? Your extraordinary knowledge and enthusiasm are as infectious as they are impressive. Congratulations!!! My wife works in science education here in Australia and she is definitely recommending your channel to her colleagues at her school. Hats off! You are my new favourite KZfaq channel and I'm already getting RSI from sharing your videos to my friends! Love your work, and so excited to explore all your wonderful videos. Live long and prosper!

"Gardena, Calif." That's old. They weren't even using the modern contraction for California "CA".

I always liked those switches. They were quite common on 70s era broadcasting gear.

Our first Mass Airflow machines had switches like that and also the BCD thumbwheel "digiswitches" for entering numeric info.

I remember watching Apollo missions on TV when I was a kid. I was in the second grade when the first one made it into space. It is amazing what they accomplished with technology that probably wouldn't even have enough computing power to play an iTune.

Love your work, Fran. Much of the technical stuff flies over my head at the speed of light, but still I find it all fascinating! Your enthusiasm is extremely contagious, thanks!

Yea, that switch module was 4PDT, and Push-On, Push-Off, you could get a diff module that was just momentary... Close on Push, Open when released... I always love the 'positive click' during actuation.... very satisfying ....

Thank you, Fran, for your videos :)

I saw this 2 years ago and just had to come back here. I used a number of these switches in the mid-70's in my electronic hobbyist craze. I used them to make an illuminated control center for my stereo system and speaker switches with relays. I got these at electronic surplus places in Minneapolis, one was Honeywell Surplus. This vid brought back a lot of memories

Wow. I once worked for the company that made that! (about 15 years later)

I salvaged a bunch of those, long long ago. The rear snaps off to allow for no switches at all (indicator only), momentary or alternate-action switches, from 1 to 4 SPDT micro-switches. Like all military/avionic displays, the lamps are front-replaceable and there are 2 lamps for redundency/safety. There's no built in lamp-test (some are push-to-test). Little silicone hats color the flange-base bulbs.

This is a MSC (Master Specialties Corp) Series 10 "Twist Light". Can be an indicator or a act as a push button switch as well. The face can be split from 1 to 4 individual segments. Can attach a switch block for 2 to 4 switches, maintained or momentary. Very common in G.E. nuclear plant control rooms. Still available new.

Incredible stuff here. I'm so happy to have found you on here. You're truly helping me scratch that tinkering itch, to an fantastic degree! Your curiosity and passion is exuberant. Thank you for sharing all these odds and ends in such detail. An absolute treat, Fran.

While serving in the US Navy as an Electronics Tech we had crude automated test suites for a sophisticated air search radar set. It used 8 track tapes to load test programs and the control panel had several of these types of switches. They always had a positive feel to them when used and having a light inside confirmed your selection when using the switch.

The same switches were used in the 1980's on offensive avionic panels in B-1B and updated B-52 bombers. I tested the panels at Boeing before they went into the aircraft. Always enjoyed pushing the "LAUNCH" button.

That's soooooo freaking awesome!!!! Thank you for your content!!!!

Awesome switch and awesome video Fran!

I have no idea what I'd use them for but I want some!

Not good enough just hooking that up... You need a whole control panel! Can you show how the labels may be put into the switches?

Wow this switch is amazing, thx for showing it!

Alternative title: "Fran replaces a bulb for fifteen minutes." Haha, Love the content, Fran. You're an inspiration!

I love this one. Thank you Fran! (Again...)

Fantastic! What a great find, and what beautiful engineering. Like you, I love this Apollo-era hardware. Fascinating.

When I was in high school, we had TONS of these in our electronics and robotics classrooms, all new in box. They were most likely donated from Rockwell, Allied Signal, or Bendix in the 80s... I helped take most of them to dumpsters when the school was remodeled in 1996. We had no idea just how special they were!

So cool Fran. I always wondered how those cool displays worked.

Keep up the great content! I like learning about mid-century tech.

Great video Fran!

You're a really cheerful character Fran! Great admiration for your analytical skills. I hope you have a great Christmas *away* from the bench!

Really interesting switch. Thanks for sharing!

Another awesome video Fran! Now I'll have to get some of these switches :)

Very nice find!

7:00 as soon as you said those color filters were flexible rubber, I thought of the semaphore I had for my Lionel train layout back in 1965. The semaphore blade uses red and green lenses made of that same flexible transluscent rubber.

Another great NASA-tech video! Thank you, Fran.

I went down a rabbit hole with those switches. The Twist-Lite series 10 switch is still available. Master Specialties moved to Costa Mesa and was acquired by Eaton, becoming Eaton Aerospace Controls Division, and more recently by Safran. Flame Enterprises at flamecorp.com has been a distributor since the MSC days and has a great collection of catalogs showing all the options.

Agreed, top/bottom split illuminated switches in COLORS are kewl! Move the color caps and use one lamp at a time for either color top independent of either color bottom!

It's gloomy outside this morning and this video is great. Anything from Apollo era mission control is worthy of breaking down. The small yet significant displays or buttons show the amazing and creative engineering. Pioneers.

Awesome video again Fran. Please don't switch subject.

Thanks for sharing

Very cool, and great video! Please it to good use, so many possibilities.

WoW. If ever something deserved a "They dont make em like they used too" thrown at it!

Thanks for this trip down memory lane. I haven't seen these since the mid 1980's when we used a lot of them at a big DOD contractor. They were really expensive, but Mil-Spec, so I've never really seen them outside of DOD stuff. The nicest part was we could just stock all of the individual pieces and easily configure them on the spot. In production the graphics were outsourced, but in the R&D labs we could pretty easily print our own or use rub-on letters.

Another great v blog Fran, keep them coming...

You’re weird and I love it. :) Also love your outro music at the end. I usually listen to the whole thing. Thanks for another incredibly interesting video!

That's the switch that got us to the Moon. Nice.

Very interesting. Beautifully made switches. Now to find more on mission control.

I believe there is a little C-frame type tool for popping the head out for bulb-swap sorta like a chip extractor, but more robust and with springsteel ends. .

That.... was awesome. Really cool engineering indeed! Loved it.

Yes they are great PBI's. I have many of them, no doubt enough to make a complete Keyset Comm module. Very ingenious Push Button indicators. Very versatile. Great video!

Another fine “Franlab” video! Fran does not disappoint.

Yesss I love this kind of stuff!

Great video Interesting design, SOLID design!! Thanks for sharing :-)

@ 14:50 "that's the wrong bulb" LoL - laughing with you, not at you. I've learned over time to check twice and replace once. You live longer that way. Good video.

What a find! You couldn't get those bulbs in quick enough. Classic excitement.

You’re right. That is too cool!

Thanks, this will be helpful.

In the early 70s I worked in the center that controlled electric power transmission throughout NorCal . These indicators were set up so they glowed white in normal condition and flashed red in off-normal condition. Two lamps for each condition. The off-normal lamps were energized through an interrupter to provide flashing. AND, the off-normal lamps had little red booties on them for coloring the light.

They make a tool to pop the lens out for bulb changes. Aviation still uses similar switches, for many different uses, but the flashing warning light is the most prevalent. I have run across older aircraft that still uses switches very similar to the one in the video. As time went on the switch mechanisms got more integrated, and then smaller. Newer aircraft are moving to different methods, especially those built in the past decade, but due to the way regulations work, older parts are still used even to replace faulty switches, rather than just install a newer style.

Beautiful piece of design and engineering.

"That's what I call engineering" I also see it as "Fran-gineering". You and I are quite similar, exploring and loving the minutiae. Great content Fran! 🤓

Very cool! Great switch and indicator engineering! Find me a switch today with this much functionality and built for ease of maintenance and longevity.

I had no idea that these were special. My dad used to buy them at state surplus by the boxful. He even used them all over the dashboard of a kitcar he built in the early 70s. I now have his boxes of them, LOL. He taught me how to open and service them, change bulbs, etc. Some are momentary, some latch. I love that you got one of them (if I had only known you were looking) :)

Thanks. Glen

Wow! That is a serious switch. Lovely!

Wow - talk about designing for maintainability... What a little work of art. It doesn't matter how deeply you dig into the 60's space programs, there's brilliant engineering everywhere. Great find and great video!

So cool seeing Apollo related items.

I love videos like this! Awesome find, and great video :)

Very good again Fran

So cool thanks

Those colours are so neat.

This is very cool. Now imagine a whole bank of these running continuously, how hot that panel would get. I'm sure those consoles had active cooling in them also.

You glow, girl!

I have seen a similar switch in a piece of equipment i tore down (it was a "Spectrascope 8000" made by LABEN, in Italy in the '70s). It was manufactured by Micro (Freeport, Ill, USA on the label) and it has a very similar, if not identical, construction to the one in the video! Same 4 (with the coloured rubber bulb cover) incandescent bulbs and switch mechanism. It was used as the main power switch in that instrument. Thanks for showing these Apollo Era pieces of equipment, fascinating stuff was made back in those days!

I love my NASA era hardware collection. We are just a few miles from Mission Control and I have a great collection of those type switches/indicators. The configurations were endless.

Great Video! In the 1950's-60s SoCal was a manufacturing and technology center.

I remember working with this sort of thing on early computers. Great video, thanks.

Hi Fran. Wow! Another amazing switch. And are they ever built - overbuilt? - which makes sense as they are "Mission" critical! Love these videos. So do others apparently. Your channel is still growing. That's good news.

Really happy to see this during Apollo 12 season! :)

I remember those switches, they were made by a number of companies and they were a pain. The lamps came in several voltages 6,12,24 and others, and the lamp covers came in a number of colors and there were various messages that went under the bezel, power, overtemp, etc. The switches came in a wide variety of combinations and some were just indicators. Oh I worked on multichannel, single channel, HF, VHF, UHF, Microwave, systems Radar, Krypto, military and after I retired civilian, it was amazing how popular and expensive those switches and indicators used to be.