ECN Forum Forums Photo Discussion Forums Electrical Nostalgia Unusual Outlet

Back on topic, what was that outlet used for?

To plug a fan into while watching the sunset !

That style of outlet was ofen used as a DC battery charger inlet on the back of older fire trucks. There was a cord connected to a battery charger with a cord cap at the station,with the receptacle mounted on the tailboard of the pumper. When the truck left the station, the cord would pull out if the driver forgot to disconnect it. I restore old fire apparatus for a hobby and many have this receptacle. I bet this was also used for DC in bldgs. Robert

I saw this in a doctors house once. The outlet was in a small room on the 2nd floor of the house, and had seperate wires going to a small room under the basement stairs. I assume that this would have, at one point, housed batteries or rectifiers, which were then wired to a radio set upstairs.

The same room also had one of those non-nema type radio combo outlets. The ones where the bottom half is for AC and the top half is aerial & ground. I think that was a later installation, though.

Interesting uses on the DC. This one was definatley 120V AC though. It was still wired to the panel with BX, still tested 120 just before I took it out.
Incidentally since my first post I have found under the house: a soda bottle from the 1920's, parts of a newspaper from 1928, a label from a box of nails stating the manufacture date in 1902, a very old roll of friction tape, a metal lid from an old Mentholatum tin and two cat skeletons.

The Mentholatum lid was right by the friction tape, I wondered if the electrician that was there many years before me used the tin for screws or something, just like many of us do today with small tins and prescription containers.

This sort of receptacle is referred to in old catalogs as a "two-wire polarity" receptacle. Apparently, at one time, the polarization of NEMA 1-15 receptacles was not considered good enough.

I have a 1930 book which strongly recommends grounding washing machines and lists three ways to do it:

1. Separate ground wire, clamped to cold water pipe.
2. A receptacle like this one, with the motor frame grounded to whichever pole is identified as neutral.
3. A "crowfoot" receptacle (probably the 20A version now known as 10-20R).

Decades ago, it seems to have been more common for receptacle configurations to be used in a multitude of different ways. We have heard that urban areas with DC service (sometimes persisting into the '50s) used 1-15 or T-slot receptacles just like their AC neighbors. And I recently saw (on eBay) a 1940's NOS 1/4 Hp 32VDC motor with a cord and 15A parallel-blade cap on it!

The 125V 15A / 250V 10A listing puzzles most electricians today, but the confusion didn't end there.

[This message has been edited by yaktx (edited 10-17-2006).]

Yup... back then Systems weren't as foolproof as they are today.
According to an old radio technician (the only person I ever talked to who has said to have known Vienna's DC system) in the 1950s Vienna used the very same non-polarized plugs for 110V AC, 220V AC and 220V DC.

Ditto in Britain. Our old BS546 (round-pin) plugs were used on both AC and DC systems well into the 1950s.

In DC areas (mostly the older downtown areas of larger towns) and Edison-style 3-wire distribution network was used at anything from 200/400 to 250/500V, with roughly half the houses taking power from one "outer" and half from the other.

Even though the 3-pin (grounding) BS546 plugs were non-reversible, there was no way to ensure correct DC polarity, as the "hot" pin could be either positive or negative of the neutral depending upon which house you were in.