Posted 2 years ago
AnythingOb…
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Things like this can still be found hanging around but also generally dis-used for decades, fastened to basement walls or rafters or out-of-the-way spots close to where landline telephone wires actually came thru a wall and into a building somewhere from the telco wires on the poles outside. They're the main parts of a thing called a "lightning arrestor" which as its name would suggest, were devices designed to act like electrical fuses -- to purposefully 'blow out' if something bad (like a lightning strike) might happen to the outside telephone wires on their poles, and thus to protect the telephone equipment and wiring that was located within the actual structure.
In the case of this one, there would have been an additional pair of slender cylindrical parts (usually looking like they're made of a reddish ceramic material with metal ends) clipped into and held between the round part and the long part, one of the clips on that smaller piece is now broken off of this one. Those things would have been the "fuses", or in other words the first thing the telco repairman would have replaced when responding to a "my telephone quit working after last night's thunderstorm" service request from a customer. The black thing in the middle of the round socket part is another level of potential protection that is also removable and replaceable ifn's the lightning would have been a "close/severe" strike, I think referred to as a "spark gap" device. The wires from the outside pole would have connected to that part first, then any/all 'inside wiring' would have continued on from the smaller piece.
It is clearly made by WESTERN ELECTRIC, the red stamped codes on its backside (pic 2) also show it is a 'model 29-B' such device made on December 9, 1919.