It's very simple if we take the ASCII diagram Andy Wade posted, with the
intermediate switch removed for simplicity and a couple of alterations:
\ red wire
C O=============red================O C
O===========yellow===========O=========== Switch return
L2 L2 black wire/red sleeve
Hall Landing Landing
switch switch ceiling rose
Now tilt your head to the right so you're looking at the diagram from
"top to bottom".
You'll see that the wiring is much simplified over the schematic you
suggested. All that is needed is twin core and earth from the landing
ceiling rose to the landing switch (i.e. the same as all other lights
with single-way switching), and then a short run of three core and earth
between the landing and hall switches. The number of wire connections
is also minimised - all connections can be made to the back of the
This way of doing it also has the advantage that it's easy to convert
any single-way installation to two-way simply by running a length of
three-core+earth from the first switch to an additional switch.
Your suggested wiring diagram at <http://www.nthothost.co.uk/assets/imag
es/Lighting_circuits_2.gif>, while it would work, would mean running alength of twin+earth from the ceiling rose to each switch, PLUS another
length of twin+earth between the switches.
A. Top posters.
Q. What's the most annoying thing on Usenet?
That's historical: in the days when houses were wired with singles in
conduit the 'original method', if I can call it that, was used. The
alternative method was then only used when converting from one-way switching
The original method is still used for conduit wiring where, with correct
layout, large current loops can be avoided.
I'd add that the way you've called it a ceiling rose or junction box would
confuse a newbie as you've laid out the terminals in a way they wouldn't
come across. A ceiling rose often confuses the first time, so I'd have
shown the terminal layout as it actually exists. And a junction box with
the more usual 4 square layout.
You've got to decide what you're aiming for - either a theoretical wiring
diagram as Andy supplied, or a practical layout.
*How many roads must a man travel down before he admits he is lost? *
Dave Plowman firstname.lastname@example.org London SW 12
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