I had one, but google quickly answered my question. What I am puzzled about is why so few people on the trains I caught during the week touched off when they left the station? My travel was in Zone 1 and I imagine most of my fellow travellers were only travelling in Zone 1, so why did they not touch off when they left the station. Simply, if you don't touch off when you leave the station in Zone 1 and you have only been travelling in Zone 1 , you pay for Zone 1 and 2.
Why did so few touch off at suburban stations?