[GreenKeys] OT: Explosion-Proof phone on ebay...

[Cory Heisterkamp]

That eBay model is what we use as our home phone. The outer case actually threads onto a cast backplate that accepts threaded conduit to maintain a sealed environment. If memory serves, the outer plastic dial operates a standard dial on the inside in a surprisingly straightforward fashion. And yeah, the ringer takes some serious current! -C

On Jan 29, 2015, at 5:06 AM, Sam Hallas <s.hallas at ntlworld.com> wrote:

> drlegendre . wrote:
>> Ok, makes better sense. But the question still remains, why must it be
>> so massive?
>> How much of what material does it take to encapsulate the otherwise
>> free-air electrical contacts? I'd think a couple of lip seals, one one
>> the dial shaft, one on the switch-hook shaft, would fairly well cover
>> it. Apparently the strategy must be quite a bit more elaborate, but for
>> the moment, the possibilities escape me.
> 
> There's an article about the design criteria for such phones at
> <http://www.britishtelephones.com/t149.htm>
> referring to the British design.
> 
> The case is designed to enclose any flame produced inside to prevent it escaping to the outside hazardous atmosphere. Note the cunning decoupling of the dial.
> 
> It's quite unnerving to dial. Having wound the dial up, as soon as you take your finger out the front plate whizzes back to normal while the dial inside the case pulses out.
> 
> Here's one in the Maritime Museum in the island of Jersey
> 
> Sam
> <P8010155.JPG>
> <P8010156.JPG>
>