I've seen these in various places in the past and I'm wondering if anyone knows what the function of it is. There appear to be large resistors along the sides of the device and an odd round knob in the middle.

I'm wondering what the two black rectangles are for


If you are in the U.S.A. I would say it is a termination point for you landline phone.

  • A very very very old landline termination point. – Tyson Nov 3 '17 at 12:52
  • 1
    There's a photo on this Wikipedia page en.wikipedia.org/wiki/Demarcation_point The knob and the brown components are old attempts at surge and lightning protection. – DaveM Nov 3 '17 at 21:21
  • Yes, my father's 1950s house had one of these mounted on the outside wall, having a punched aluminum housing with "Western Electric" embossed upon it, and a large grounding wire bonded to a ground rod driven into the ground. A telephone lineman told me it was for "lightning protection" of the phone line. – Upnorth Nov 4 '17 at 6:00

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