It holds the brake for hill starts, for example, if you are leaving a station that is on a steep upward hill/gradient, you can hold the brakes to prevent the train rolling back upon departure, hope this helps
On a train with air or vacuum brakes, it's like opening a tap - opening wider means pressure is applied quicker. Hold means you keep the brakes at that application of pressure, without increasing or releasing it.
I don't think you'd need to do this - which trains have pressure systems but not a strong enough torque to move off on release?
That’s correct for UK trains, which is what I assume the question was about. On trains with a single lever for power and brake the power doesn’t start applying until the brake is off, so the brake hold button is used to hold the brakes on until enough torque is generated to move off. Without this the train would roll backwards. It’s on many UK trains and is used extensively. Isn’t that normally called the lap position? There is a hold position on some trains that holds the brake cylinders on but allows the brake pipe to return to pressure but there aren’t many of those in TSW. I can only think of the F40 that has that off the top of my head. I don’t think that was what the question was about though, as it was most likely the brake hold button on UK trains. It is still used. There were two different systems being discussed. You were correct.
Actually nope, you were more correct - I was thinking of TGV systems and applying it to air brakes, as Stu has pointed out above. He and you are right
Fair enough, I am familiar with the Sprinters and Pacers where it was left in notch 1 until that point, which I imagine means the same thing? Thanks for the correction