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Post by elorens on Oct 9, 2020 8:35:53 GMT 12
Can you identify this object, found above a hot water cylinder in a 1950s house? My guess is that it’s some kind of safety device. If so, we have the irony of a safety device mounted on a piece of asbestos... Thanks Lawrence
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Post by dada on Oct 9, 2020 9:12:04 GMT 12
In the distant past before fibre to the home, there was POTS – plain old telephone service, provided over copper wires. Before these were undergrounded in cables, copper wires on overhead “aerials” ran along streets on poles like power wires in some places. As these aerial wires were exposed to the elements, lightening, other power wires and the likes, the home and telephone instrument was protected by that device you see on your wall. The outside wires (lower portion of your device) first encountered a carbon / mica air gap to a ground wire (normally the centre of the lower circular device) before connecting through the two parallel rods (that are actually fuses) to the household telephonic device. The idea was that the carbon/mica spark gap took most of the blast from say a lightning strike and the fuses blew if there was a power contact. Needless to say, lightning strikes have considerable energy and the asbestos board was a measure to prevent a fire. Nowadays of course underground cables make such devices relatively obsolete, and fibre to the home provides a complete redundancy of the device. However, it looks as if your device has relatively recent connections (white wires at top) so unless your telephone service is now connected via fibre (along with your internet) I would suggest it may still be in use. The simplest way to check this may be to remove one or both of the fuses and see that the telephone still works!
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Post by elorens on Oct 10, 2020 9:12:00 GMT 12
Thanks - very interesting! The services are all underground in this area, so this device seems redundant. Would it be significant that it is mounted above the hot water cylinder? Maybe a path to earth there?
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Post by Radiotech on Apr 12, 2021 21:48:44 GMT 12
Thanks - very interesting! The services are all underground in this area, so this device seems redundant. Would it be significant that it is mounted above the hot water cylinder? Maybe a path to earth there? They were normally mounted in the hallway and towards the front of the house. They have been redundant for many years, long before telco services were undergrounded.
It reminds me of my time in the TV repair game many years ago when I used to do housecalls. I wsa contacted to go and look at a TV which had been on during a lightnight storm and was now dead. Upon entering the customer's house I noticed a very black explosion mark on the wall and a large crater in the centre. I asked as to what had happened. "That's where the telephone used to be - the lightning blew it clean off the wall and pretty much vaporized it".
I don't think even one of those fuse blocks would have saved that phone.
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