enter image description here

Is it something to do with the doorbell? House was built in 1947 if that helps.

1 Answer 1


That device is a telephone line fuse and surge protector device. The fuses are in line with each of the two telephone line legs. Inside there will be a spark gap to shunt possible lightning on the line to the third center GND wire on the one side.

These were common in the vintage days when most telephone service was delivered via open wires overhead on poles. These days they are mostly redundant now that most telephone service is delivered underground or may enter the premises through a telephone interface box. These boxes have the surge protections built right into the interface box.

These days when some folks that still use wired telephone service and also use that service to receive internet service via ADSL or DSL it would be necessary to evaluate the installation to see how the line surge protection is provided. If it is handled by one of these vintage style surge protectors it may be necessary replace devices like these with the more modern style interface box and surge protection to allow the ADSL/DSL signals to pass without attenuation.

  • 3
    Wires on poles are still a very common delivery method - perhaps not in your neighborhood; but your neighborhood is not the world. DSL certainly works with the newer style of line suppressor, and it's irresponsible to suggest removing one of these that's in service without replacing it with a new one - all telephone lines, including underground ones, are subject to surges and need suppression - in a new install that's in the telephone interface that is now commonly placed on the exterior of the house. -1
    – Ecnerwal
    May 22, 2015 at 12:54
  • @Ecnerwal - I am editing the answer to change the tone of the removal comment.
    – Michael Karas
    May 23, 2015 at 9:23
  • 1
    Thanks - thats better. +1 Having had phones on underground lines with suppressors smoked by lightning induced surges anyway (modern prissy ones, not Western Electric tanks) has made me a big fan of fiber optics - but surge beats no surge.
    – Ecnerwal
    May 23, 2015 at 12:54
  • If this device is NOT in use, it can be removed. Otherwise, I suggest you leave it. May 27, 2015 at 18:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.