Can you figure out what technology is in this 1929 photograph?


The huge thing in the foreground to the left is a series of batteries in parallel. I am going to guess that the thing at his feet is another battery. That is all I got I reserve the right to be wrong.


Ha-ha! “series of batteries in parallel”; good one. I was focused on the newfangled bulletproof hair laquer that doubled as shoe waterproofing.


Haha, that is definitely the early Internet! Nice find!


Looks like a bunch of batteries, tubes and a transformer, probably a signal amplifier of some sort. Maybe an early telegraph, radar, or radio station? The big cement thing in front of the guy could be the base of a dish if it were that kind of broadcast.

1 Like

That looks like a large bank of Leyden Jars (a primitive capacitor maybe for a spark gap transmitter ( (edited so second link is a link)


The MST3K guys would probably shout RADAR!


Yep – looks like a honking big spark gap transmitter.

Ok – Left side table – far left leg: the white cylinders are 100W+ resistors of a type made from nichrome wire wrapped around a ceramic tube. They are fitted vertically, clipped in like fuses.

The left table has two layers of six banks of either voltaic cells or leyden jars in a loop (2x12). At the right side (front) of the table are two x 6 sets of knife switches, likely to engage the upper/lower banks as needed (12 switches). The wooden box on the small shelf may be incidental, but just below it is a pair of fuses mounted in clips. I suspect they are leyden jars because the table is wired to a 6 Volt battery left of the man’s foot (only 3 cells, so only 6V). The presence of the huge resistors would allow a safe way to drain the leyden jars as needed, and the battery would feed them to store some huge charge for a discharge on demand. Note how heavy the side cabling is, probably cloth/knit insulation as was common in that day. On the ground between the two tables is a light strip showing four sockets and two bulbs, not wired in parallel or series – they are for a particular setting. Light bulbs commonly provided a resistance source for radio units when you didn’t want to transmit but the energy had to go somewhere, so they may be serving as a tuning dummy load.

Note the horizontal tube above the man’s right wrist – the slide bar and knob above the tube suggest this is an inductance tuner, made by a wire wrap around a tube with a sliding pickup to vary the number of coil turns in the circuit. This sort of this in common in making an old style crystal radio, and is used to tune the desired frequency.

In the big box the man is touching are the tops of four very large radio tubes (valves in the day), and the two squarish things sticking up on the left side might be the ends of some capacitance plate tuners. The decorated box at the back right of chest – no idea.

What I’m not seeing is a telegraph key or bug, though the white object just above his right elbow might be the side or end of a bug-type key facing away from the camera.

Not sure what the other objects at the far end of the table are.


By 1929 broadcast radio had been around several years. Electric microphones too. Crystal-controlled oscillators too. Spark-gap had been history for 15 or more years.

Set up on some roof outdoors. There are no antenna feeders of any kind, no visible microphones or headphones. Those big wooden cabinets contain audio and test gear. The wires are cotton-wrapped like most household wiring. Some wires drop down to (probably) more gear behind the seated geek.

Inside the big box is a “Bright Star” (est. 1909 in PA) “Radio Battery” (non-rechargeable) # 30-95 B-battery (anode voltage supply). Vacuum tube devices used A, B and C batteries back then. Also in the box are the tops of 4 big tubes and a couple of cans. This may be an audio amplifier.

Consider the amount of current those big batteries of individual cells in the foreground could produce. MANY hundreds of amperes. The knife-switches on the side allow ganging for different voltages. This is not a radio transmission; this could be either a live remote setup and/or a public-address system. Considering the geek’s clothing, this is an important event.


I agree that it is audio, not radio. I’ve built a lot of radio gear, and looked at a lot of old radio gear, and there is no sign of any radio frequency components at all in this photo.

Public address is most likely.

I would also venture to say that it is part of the public address system that was used for the Hoover inauguration that year. Probably somewhere on top of the Capital building. Or I could be completely wrong.

sparkpunk technology?


This is what 1920s radio components look like.

1 Like

I am guessing Leyden Jars capacitors or batteries. Looks like they are in banks. Each bank is series fed. I am guessing that the knife switches switch in each bank. This could be used for tuning in the case of Leyden Jars or switching in various battery banks such as edison batteries. Suspect more the Leyden Jars.

Umm… whut?

It’s Tintin toying with Professor Calculus’s sound wave focusing device at Marlinspike.

Stand back from the windows.


Who says battery technology hasn’t come a long way in a century? That huge battery probably doesn’t produce more output power than today’s cell phone, and a battery that size can power an automobile now.

The fool has forgotten to attach the Interocitor!

  1. Anyone else notice what’s standing against the wall in the background? Look between the struts, directly above the operator’s hand. Looks like a bomb, with fins for dropping from a plane (or airships as were still being used at that time).

  2. In the foreground, those huge banks of capacitors - if they are that. They are connected in series, not parallel. This lowers the capacitance but raises the voltage. But given the geometry, a high voltage would cause arcing at the supply wires at the terminals, so this doesn’t make sense. I’m suspecting those are also batteries, to provide a high-voltage DC current where regular batteries (such as the one in the wooden box or near the operator’s feet) won’t do for some reason.

  3. I think I see a wire recorder edge-on also directly above the operator’s hand. (Between the hand and the “bomb”.)

  4. Notice the strange shape of the panels on the top. Could be a “funnel” for radio waves.

As other commenters have noticed, much of the typical period radio gear is missing, but only if you consider commercial/ham radio. My guess would be that this is a radio receiver for other types of waves - either early RADAR type experiments or Radio astronomy, with the main antenna mostly out of the frame on the top.


Just looked it up, and there was a total solar eclipse May 9, 1929. This may have been an experiment about the effect of eclipses on radio.

1 Like