> Thanks for the explanation

No worries.

Note that this type of remote signalling can be susceptible to external
electrical noise as, because of the resistor, the wiring has fairly high
impedance and can act as an antenna and because of this it's often
recommended to use twisted pair cable to minimise common mode
effects

http://en.wikipedia.org/wiki/Twisted_pair

or a current loop

If the signal is encoded and some error- or majority-checking is used
then it's not such a big deal. One project of mine used IR transmitter/
receiver ICs on a two-wire system and I can't say I noticed any real
problems with single-strand figure-of-8 bell wire, even when switching
lights and relays

Joe
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