On (27 Jan 97) Frank Malcolm wrote to Roy Mcneill...



 FM> Hi, Roy.



 RM>  BV> I had a close look at where the light switches were as you moved

 RM>  BV> through the house, and made some of them 3-way and one 4-way

 FM> instead

 RM>  BV> of just 2-way.



 RM> Hmm. It's easy to use a simple spdt switch to do an even number (2

 RM> way, 4 way, 6 way), but to do odd numbers needs 2 pole switches.

 RM> I'm out of touch here - are 2 poles readily available?



 FM> Now that can't be right. Assume that you could do 4-way with spdt

 FM> switches, and you want 3-way. Just wire up 4-way and hide the 4th

 FM> switch. Then think, shit, that 4th switch isn't doing anything - I'll

 FM> just hard-wire it.



Good logical point, with only one flaw - my original logic! I've

just redone the circuit on paper, instead of in my tiny mind. A

dual switch can be done with two SPDTs, any more can be done with

an SPDT at each end, and any number of DPDTs in between. Two wires

run the full length of the chain of switches. The SPSTs switch the

single incoming to one or the other wire, the DPDTs just swap the

two wires over.



Cheers, and ta...



--- PPoint 1.88