Ed Durrant replied:

Phone lines are usaually 600 Ohm impedance, co-ax on the other hand is 50 or 75 Ohm.

I'd try it since it's there - the worst that I would expect is that the volume on one or both phone units will be lowered and if that's the case you can easily disconnect the cable. Chances are it'll work fine.

Hello Ed:

I think I need to describe the situation a little
more clearly, given your reply and several others.

..................................................

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So, thank you all for your suggestions and
thoughts on this rather confounded question!
I'll try the installation using the coax and
revert to replacing (or adding a run of phone
cable in parallel with) the coax if it does
not work.

Again many thanks! There is so much knowledge
available on this list!

- Mark

Mark Henigan
--

Mark - I think in this situation, where this is going to only have your office on the co-ax, I'd certainly say try it ! There's a good change it'll work.

Am I right in assuming that the co-ax is not run through some sort of trunking but rather, simply fastened to the outside of the house ? If it does use trunking, you could use the co-ax cable as the "draw-cord" to pull the phone cable trough to where you need it.