pax britanica. ... Thank you very much for your detailed reply, fills in a lot of gaps for me ! 4 and 7 aren't necessarily my problem, I just used that as an example, but maybe two keys in close proximity may give a problem of crossed connectivity - maybe. Never say never.
I hadn't thought about the length of time taken for the old rotary dial to transmit a 9 or a 1, and maybe that is why the NZ Police use 111, but I think that the ability to find an easy digit, or key, in the dark or reduced visibility, e.g. heavy smoke, outweighs a few seconds gained, which is why the USA 911 is illogical, one has to stop after the 9 and find the 1... but then who said the USA was ever logical, look at their date formula, small,medium,large or large, medium, small makes sense, but medium,small, large. i.e. month, day, year is illogical. ( and no, I'm not starting another Yank bashing contest - wouldn't dare, I'm married to one ! )
Cheers and thanks again.
ExS.