Thanks for the quick response.
The last time I used it, about 10 yrs ago, it was functioning fine in respect of running trains, on an indoor layout, though I didn't get round to getting points/signals wired up before the OH decided we were extending/reflowing our old house and the layout got dismantled/packed away.
I appreciate "proof of the pudding" will be getting this built and then seeing if it will actually work. Seems from your reply that in theory at least no reason it can't control a garden railway.
I can't recall the specs, but think Z1 put a permanent 18v current through the tracks; I certainly remember getting a buzz when leaning on some live rails when I first used it all those years ago.