I can't remember about the 197s, but some UK CAFs have, following the standard European model, separate emergency call and emergency brakes. The former alerts a member of staff but doesn't cause a braking demand (basically the same as the toilet call for aid button), the latter does cause a braking demand. The former is typically a standard door style button with a bell embossed on it for blind people and the latter a handle or break glass.
Obviously using the former by accident is low consequence, just mild annoyance for the guard, because it doesn't delay the train and doesn't require physical resetting - it is in essence just a telephone, more like a station help point.
While it does mean someone has to make a decision of which to use in an emergency, this (which is standard across much of Europe) does have something going for it, in that if the emergency is medical, for instance, the train will reach a place an ambulance can get to more quickly as it won't waste time stopping in the middle of nowhere while it is reset, whereas if there's something physically wrong with the train e.g. a derailed bogie or open door you can use the emergency brake because stopping is a priority.
It also means there's less imperative not to use the call for aid button if for instance the guard is hiding in the back cab and e.g. a lone female or child is in a staffless second unit and is panicking about having missed her stop and doesn't know what to do. It would clearly be misuse to pull the passcom and stop the train for that, but using a call for aid button for it doesn't feel inappropriate to me.
Whether this is the European standard because of retrofitting passcoms to stock that only had an actual emergency brake tied into dumping the brake line or whether it's because of deliberate design decisions noting the above advantages I don't know, but it seems a very good setup to me.
