Pictures and info supplied by napervillesoundtech:















Thanks Ben.




[This message has been edited by Trumpy (edited 10-21-2006).]

Ben,

I too shudder to think that this may once have been part of a school curriculum, but such parts were once common. Well into the '20s and possibly even later, knife switches were standard for service equipment, and cleat lampholders such as those shown here were in common use.

Even today, the NEC allows cleat lampholders with exposed live parts, if they are located a minimum of 8' above the floor! Needless to say, I would never install one.

And those single-pole knife switches? I visited a church in Mexico in 2001 that had those for lighting, in public areas, at customary wall-switch height!

Some of the switches are single pole, the "main" switch is a double, switching both the hot and the neutral. This has one of those old, non-deadfront type rubber plugs on it, which is not polarized. I agree, I wouldn't want to install one of those lampholders, either. They are also hard to find in stores, I have noticed, although I have never tried to order them from a supply company.

I've bought a few from Home Depot and/or Lowes; but they only sell the plastic types.

I've seen the porcelain varieties in lamp-parts stores and independent small hardware shops too.

Knife switches, while still common, are now these little plastic things, about half the size of that. Another easily found item.

Consider the possibility that this might have been used as a crude load bank for who knows what. You could use something like that to check regulation on a LVPS, for example.
Joe

Quite possible it was used as a series load bank.
I use 2 x 100 watt lamps parallel in series with an appliance under test, especially for radio's, tapedecks and the like to have a limiter in case of a dead short at a faulty appliance.
I take one lamp out depending upon VA rating of appliance under test.
I like to see the porcelain fittings, a lot more durable then the plactic c%@p we get now these days.

I don't. In the era that this device would have been found in use, both adults and kids had more common sense and maturity. It would have been a very effective demonstration of the principles of current flow and what-not.

I have always been a "tactile" type. Show me a schematic, and I can work it through with some difficulty. Show me the actual device first, then I can not only read through the schematic a lot faster, I can draw one up!

Or a better example, I designed a dual-motor control with delay start for motor #2 for pipe organ blowers. I built it first, then drew out the diagram by hand after in about an hour. It would have never gotten built if I'd tried to draw it up first.

I flunked chemistry in High school for the same reason. Give me the chemicals and lab supplies and I could solve any formula. Give me the book or a list on paper, I couldn't get the formulas right to save my life! Really ticked off the teacher and my parents!

I guess this a little off topic but concerns how people think about things. Several years ago I was sent a file named "brain.exe" You answer a series of questions and it performs an analysis. Everyone at work gave it a shot and found it to be interesting. If anyone wants to check it out, email me and I will attach it to a reply.
Joe

You all bring up a good point I hadn't thought of. Assuming that you are cautiouss and do not touch any live parts, this wouldn't be that bad. I am mostly thinking of people I went to school with who would grab part of it "just to see what would happen" An electronics/electrical class can be very scary sometimes.

I imagine something like that being on a teacher's desk, with the students watching from some ten feet away.

I vaguely remember seeing something like this in my grade 7 or 8 shop class in the early 1970's. If I am not mistaken though ours were powered by a big lamp battery instead of electricity.

Our instructor used it as a visual thing to show what the textbook was talking about.

Things like parallel and series circuits and three way switches. He always picked somebody to come up and wire it at the end of class.

I agree entirely. If it were being marketed to 6-year-olds to play with alone, then there might be cause for concern, and a harmless battery-powered version would be far more appropriate. But items such as this (and the resonance demonstrator in the other thread) were clearly designed and build for class demonstrations where there would have been suitable supervision.

It seems to me that these would have been set up on a bench and the class gathered round to watch the demonstration. In fact we did just such experiments when I was in school in the 1970s, both physics and chemistry.

If we're going to insist that the equipment is completely covered and idiot-proof, then we'd better not let chemistry students handle bottles of hydrochloric acid. Better not let the girls handle hot cake trays in cookery classes either (if they even do cookery these days!).

Remember prior to the 1970s we had an entirely different legal system. If you were a student and were stupid enough to touch a live circuit board like that not only did you get a good shock but also a smack in the back of the head by the teacher for being an idiot!

Let's see how that would be today.

We would sue the school district, the manufacture of every part on the project.
including personally the board members of those companies. The teacher would be fired. The school principal would have to resign along with the disrict superintendent due to media pressure. Electricity would be banned as a science topic.

Did I miss anything?

[This message has been edited by Gus99 (edited 05-03-2006).]

Could it be an elementry level logic device?

This from n1ist:



Here's the schematic:



I'm not sure why the 4 bulbs are all in parallel without individual
switches; that would have made it more useful. Maybe it did double as a load bank.

Maybe the designer wanted a fair-sized fixed main load in comparison to the bulbs which can be switched into the circuit in series and just hardwiring four lamps together meant that all bulbs could be the same wattage for simplicity.