On Thu, 12 Dec 2013 20:15:33 -0000, Chris Hogg wrote:

On Thu, 12 Dec 2013 19:47:20 GMT, The Other John
wrote:

On Thu, 12 Dec 2013 19:12:58 +0000, mogga wrote:

We're getting some new street lights and have noticed they have little
antennas on the top.

What is it for? They look like they have a light detetctor same as the
old ones too.

They are remote controlled and dim-able, we've got them too.

TOJ.

We have them here also (West Cornwall). Many years ago, say in the
early 1960's, the street lights here were switched on from a control
centre in Redruth. A pulsing audio-frequency signal was sent through
the mains supply (about 1 pulse per second IIRC), which set a sort of
balance-wheel arrangement oscillating in the control box in the
lamp-post, until the amplitude got large enough to close a contact,
switching on an individual light or short sections of lights. The
slight variation in characteristics of the oscillating switch meant
that the lights didn't all come on together, but over a period of a
few seconds, so reducing the sudden drain on the mains supply, AIUI. I
used to have a Cossor CR100 communications receiver*, and obviously
something in the power supply wasn't very well screened, as I could
always hear when the street lights were being switched on. There was a
greatly enlarged model of this oscillating switch on display in the
Science Museum, which worked when you pressed one of the buttons that
were on every display case.

* http://www.shopingathome.com/images/B28.jpg

Adding crap to the mains supply is not a good idea, as you found out.

--
Why do the Scots wear kilts?
Sheep can hear a zipper at 500 yds....