Didn't hear it myself, but...
During the summer we took delivery of our (ahem) "new" Cl317/8 StanEx units. You know the ones; exactly like they were before going to Wabtec, but now painted bright blue. Anyhoo, one of the innovations on these is a PIS system with LED destination indicators and screens inside the coaches (although the initial configuration for the system was just for the external destination indicators only). These worked great for a few weeks, after which they all appeared to melt in the heat and stop working. Any code you entered would give the error message "Incorrect Code".
Feeling a trifle bored whilst waiting at STN I decided to go on a "fishing expedition" to try and prove that the PIS wasn't actually broken but just a bit confused. So, I start hammering in codes almost at random and getting nowhere. However, after a few minutes I strike gold when the internal display brings up "SWT Demo". So, as this is the first code I've stuck in that hadn't come back incorrect, I accept it. Stroll outside and have a look at the front and, sure enough, it says "Clapham Jn" on the front of my train.
The problem was that, having got this up, I couldn't then get rid of it. But then, given that no-one pays the blindest bit of attention to what it says on the front of the train, I decide to ignore it for the moment and sort it out when I get to LST.
All went well for a while. I stopped at Bishops Stortford and no-one seemed to look twice at the destination. However, as I was going down to Tottenham Hale I notice that the PA light keeps going on for a few seconds every few minutes. I try and buzz up the train host on the intercom to find out what's going on but I can't get any answer, so I decide to leave it until I get to Tottenham Hale.
When I get there, I try the intercom again with no luck. In the end, I had to ask the trolley-dolly who had got off there what was going on. "Oh yeah", she says. "It's announcing that the train is for Clapham Junction". At this point the train host comes through into the cab and is not looking best pleased. It seems that he'd had to explain to everyone (almost individually) that the train really was going to LST in spite of what the announcement was saying.
I didn't even know that the PIS we had would do this. So I quickly make a PA and blame it on a fault with the PIS.
one TN