[GreenKeys] Open lines?

[Sam Hallas]

amourdutigre wrote:
>  I have been perusing my copies of the greenbooks, (I have the last
>  two, and am shopping for the first two), and was fascinated by the
>  fact that the longlines engineers would phantom a third call upon two
>  pairs of open lines. I have several questions about this.

>  First, are there anymore open line circuits still in operation?

I can't speak for the US but there are open line circuits on rural 
railways in the UK.

>  Second, if there are say four pairs of wires, ("sides"), could you at
>  least theoretically phantom up to six other calls on those four
>  wires? One phantom circuit between each possible pairing of pairs so
>  to speak.

If you think about it Joe, the answer must be no. It would be like 
saying you could make six circuits with four wires - 1&2, 1&3, 1&4, 2&3, 
2&4, 3&4. The circuits that share a wire interfere with each other, 
which ends up being all of them.

However, it was practice to generate a phantom on a pair of phantom 
circuits. So your four pairs could generate two straight phantoms and 
single double phantom. So your four pairs could generate seven circuits. 
I recall that making phantom circuits work properly over long distance 
required great attention to wire transpositions along the pole route.

Cheers,
Sam