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VINTAGRAPH • WPA • WWII • ABOUT PARIS, 1895

Dial D for Danger: 1919

Dial D for Danger: 1919

Washington, D.C., circa 1919. "Chesapeake & Potomac Telephone Co. equipment." Harris & Ewing Collection glass negative. View full size.

 

Modularized

Interesting to see the modularization of that panel so early in the game. Very logical. Each module with a tube inside has associated jacks so that a meter box can be used to quickly check operating conditions.

The PA idea makes sense considering the connections for "long line" and "phonograph." Four tubes that size might realize a 1000-watt system.

Public Address System

That appears to be an old public address system with the capability to attach and simulcast over the "long lines" of the phone system. "Loud Speaking Receivers" would be bullhorns. Both consoles are nearly identical. Each console has four tubes with inputs to drive 1&2 and 3&4 separately.

This appears to be a system operator position, and not the position one would speak from. A microphone and a headset earpiece are between the consoles and are connected to the small box between them, not to either console. If I'm right, then the mic and headset would be to coordinate with the other half of this contraption -- probably near the speaker position and/or the other side of that "phonograph circuit."

re: Phonograph circuit

For making a transcription of whatever they are getting via the telephone circuit. Note that it has an 'output potentiometer.'

As Dave hinted previously, 1919 was a few years ahead of regular broadcast radio (although not some experimental stations) but perhaps this was so audio from entertainment or political events could be sent cross-continent and preserved or distributed.

Having that 700 volt plate voltage (if that's indeed the case) still puzzles me. Something in the range of 150 to 200 volts is more like it for 'normal' amplification circuits. There surely would not be a vacuum tube circuit with 700 volts on the plate circuits unless it was producing several hundred watts of output. If not an exciter stage for a broadcast transmitter, then next most likely would be a massive public address system.

Were there public gatherings back in that era where they'd commonly need such power AND this telephone equipment? Perhaps political conventions? I am very intrigued by this device.

Phonograph circuit

So why is there a "Phonograph cct"?

Danger: Yes!

Watch out for the carbon tetrachloride fire extinguisher; it's poisonous.

Knife switches and quarter-inch jacks

I'm just amazed at the number of porcelain-based knife switches that were used in the operation of the equipment. In looking closer you can see quarter-inch jack plugs, commonly called "phone" jacks. Which went on to become the standard for broadcast patch panels and guitar amplifiers and cables.

The vacuum tubes

in the amplifiers probably had 700 volts on their plate circuits.
My father's first ham (amateur radio) license was issued to him in 1919 and I remember components in our home that looked similar to those pictured.

Details, details

Click to enlarge. Then click the resulting image to expand it.

Danger!

Shocking, isn't it?

The latest equipment

Of course it wouldn't be complete without a cuspidor.

Essential equipment

A fire extinguisher, and what seems to be a cuspidor. Furniture by Flintstone and Rubble.

Spit-ding

"Leave your message at the tone"?

But seriously, an odd device, with "speaker and long lines cct" (circuit), "phonograph input" and "700 volt fuse" markings.

I hope someone can explain the function of this setup.

Perhaps used to feed a radio station live "remote" broadcasts over telephone lines and the high voltage & power amplifiers are used to drive the transmitter?

[Not in 1919! - Dave]

Under the Capitol?

Looks like a temp facility in the same general location as this..

http://www.shorpy.com/node/5384

Maybe under the East Front? The columns give it away..

Pre-miniaturization!

Fascinating glimpse onto transitional technology. I wonder if a higher resolution scan would allow the label to be read and some of the functions determined?

Lots of selector switches, several knife switches (looking like telegraph keys), some mics and one big honking speaker. And some lovely woodwork!

Ding

Very hi-tech stuff I'm sure, with the obligatory spittoon.

 
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