At the start of a route, the driver puts a PIS Code in on a 185. This 4-digit PIS Code appears under the first line of the service he is driving printed on the docket.
At any time, the guard or driver can select additional non-standard announcements, such as....
Please have all tickets ready,
First Class Front
First Class Rear
Trolley
Delay / signal failure
Smoking
Delay / failed train infront etc
....and many more including.....
Major incident, all staff have left the train, stay on board,
Delay fatality,
There is the facility to pause the normal (GPS-based) announcements, at the point they become annoying. There are also a range of silent codes which display the Destination only, with no announcements, useful for night services where proper manual announcements are often more appropriate.