Many thanks to all who sent answers.

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From: CA
Date: Wednesday, January 03, 2001 8:16 PM

It looks like a thermostatically controlled heating element ----
perhaps that contact opens up when the heating bars get very hot.

From: DH
Date: Wednesday, January 03, 2001 8:37 PM

Bi-metal circuit breaker ( interrupter )

From: Tom
Date: Wednesday, January 03, 2001 8:42 PM

It looks like an early version of an entrance fuse box for a telephone
line. The long components, at least in the newer units, are fuses. As to
the mica stuff in the can, looks to bee some kind of lightning
protection, the lightning induced voltage would arc through the mica
material to ground. Kind of an early day surge protector...

Even in the early days, they had "tip" and "ring" lines. THese terms
referred to the tip and ring on the universal 1/4" phone plug...

I work in technical support for a large access control and residential
alarm manufacturer and have heard horror stories about appliances like
that and the noise they cause on phone lines. Of course the fact that
the system won't communicate with the monitoring station is ALWAYS the
fault of our equipment, NEVER the customer's phone system... :>))

BTW, except for what I believe to be the lightning arrestor, the newer
units are surprisingly similar (some units use an open air gap with two
pointed metal electrodes facing each other with a ground electrode
between them. The idea is that the lightning should jump the gap to
ground, the path of least resistance, and all that <g>). That is only
true in theory as anyone who lives in lighting country knows, lightning
goes where ever it wants... :>))

--------------------\               /----------------
                       \          /
                Line /    0   \ Line
--------------------  /     |       \----------------
                         | | |
                         | | |
           | Ground Electrode |
                           | |

I tried to find a photo of one on the Internet and include the URL with
my answer, but no such luck. Just look for a box on the outside of your
house where the phone line enters. If you open it up, you'll see the
porcelain insulators and two cylindrical fuses that are about .5" in
diameter and about 4" to 6" long. I don't know what they use on
underground feeds, probably quite similar though...

From: LH
Date: Wednesday, January 03, 2001 11:06 PM

I'm guessing a capacitor, with the mica acting as an insulator.

From: EP
Date: Thursday, January 04, 2001 3:33 AM

Those reddish tubular assemblies have the look of old Western Electric style telephone fuses. But that copper block assembly doesn't seem to be anything but a short circuit.

But then, maybe you could have shown those 4 blocks better. Two blocks on each side, but something else between the block pairs. A mica sheet?

And the screw-on cover for the block assembly. Curious. Do I see holes at the bottom of the cover?

From: JGM
Date: Thursday, January 04, 2001 7:27 AM

Looks like a telegraph clicker to me...

From: SF
Date: Thursday, January 04, 2001 11:01 AM

It's a POTS (telephone) building-entrance 'surge' protector. The red tubes are, indeed, fuses.

From: TL
Date: Thursday, January 04, 2001 11:15 AM

Mike,
What you have there is a telephone station protector from the early
part of the 20th century. The two fuses were rated at about 7 amp.
These provided overcurrent protection. In the center of the round
porcelain part there are two carbon blocks with a 3 mil. gap. These
provided a path to ground for spikes such as lightning.
When these were in use, the telephone repairman would spend the
better part of the day after an electrical storm going around replacing
the fuses and carbons to get subscribers back into service.
There were still some of these in service when I began my career
back in 1970. Most, if not all, have now been replaced with Network
Interface Devices (NIDs) that have gas tube or solid state protection.

TL
General Manager
Palmerton Telephone Co.
Palmerton, Pa.
Serving the beautiful Blue Mountain valley since 1900

From: JT
Date: Thursday, January 04, 2001 12:26 PM

I remember seeing one of those on the wall of the house I grew up in (long
time ago). I was told it was part of the telephone system.

From: EHS
Date: Thursday, January 04, 2001 1:12 PM

I believe the device is a fuse and arc supressor, and was used on the
telephone lines.  If a large surge came into the house on the phone lines, it would arc over and blow the fuses.

From: Sam
Date: Thursday, January 04, 2001 1:42 PM

it's an old type telephone interface...fuses and the screw in thing is
for the lightning carbons.
nice picture...
my best, sam

From:RM
Date: Thursday, January 04, 2001 6:27 PM

phone line equipment. used for lightning protection
the third terminal ao the right side would be tied to earth.

From: TDH
Date: Thursday, January 04, 2001 8:15 PM

This is a carbon block lightening protector for telephone lines. The
carbon blocks are the parts under the cap that is removed and lying to
one side. The two long red things are fuses used to guard against
excessive current entering the protected premise on the phone line.
There are many thousand such units still in service in older homes.

I think you will find that the electrodes are copper but that the
blocks between them are carbon. There are three electrodes consisting
of tip (on left with fuses down), Ring (on right with fuses down), and
ground (in the center). These are separated from each other by carbon
blocks. The blocks become conductive at high voltages thus shunting
lightning induced surges to ground. If the blocks were copper they
would short out the phone line. I believe you will find these devices
are still in use in many thousands of installations. Good Luck.
--
Tom of the sparks and arcs

"This alternating current thing is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

From: TL
Date: Friday, January 05, 2001 5:43 AM

Go right ahead. I've never seen copper protector blocks though. I guess
they would resist dusting better than Carbon. That was also a problem.
Little bits of carbon dust would flake off over time and bridge the gap.
Then ringing current would shunt to ground and cause false ring trips. Over
time the shunt would worsen causing a hum on the line if on the tip side or
a loss of service if on the ring side. The gap, by the way, was 3 mil.
(0.003"). 3mm would probably be too great for a voltage as low as 250V to
jump. Some blocks had one piece of solid Carbon and the other of porcelain
with a small Carbon insert in the center.

Tom Lager

Palmerton Telephone Company
Serving the Beautiful Blue Mountain Valley
Since 1900
WE WERE DIGITAL BEFORE THEY WERE EVEN BORN

From: Andy
To: <mgr@zocalo.net>
Subject: Electrical Gadget!
Date: Friday, January 05, 2001 4:31 PM

hi

I think that is not a fuse but a regulator for a electric device like a lamp or motor. May be a foot pedal for a electric sawing machine?

From: "Robert
Date: Sunday, January 21, 2001 8:16 AM

(thanks to Robert for this complete explanation of how the gap and fuses work together - mgr)

I've seen a somewhat newer version of the fuse gadget;
it was used on the house I was living in around 1960, and
replaced then.

It's the fuse and spark gap assembly for a telephone line.
The two long cylinders are the fuses. The copper mica
assembly is a pair of spark gaps. If the copper blocks
touch when assembled, some of the mica is missing;
they should almost, but not quite, touch. The black object
in the middle is probably part of the ground wire, and
connected to one side of each of the two spark gaps.

It would normally be inside a metal box on the outside
of the house when in use - unless the ones that old were
housed differently.

Its purpose is to protect the telephone from lightning and
power crosses (telephone wires touching power wires).
The spark gaps (connected to a wire to a metal rod
driven into the ground, and to the telephone) would allow
a spark to jump across the gaps whenever there is too
much voltage, and therefore limit the voltage to the
telephone. The outside phone line, to the telephone
pole, would be connected to the other end of the fuses;
the sparks would allow enough current to flow to blow
the fuses. In normal operation, of course, there would
not be enough voltage to start the sparks, so the fuses
would not blow.