that’s the phrase used here in berlin for please stand clear of the doors. in case you’re interested there is a youtube video with all kind of sounds of berlin’s rail-borne public transport system. the magic happens at 0:32 and does not stop there ;)
the picture shows part of an abandoned supervisor’s booth at u-bahn station schlesisches tor in kreuzberg (cf. video at 0:46)
.documenting.the.obvious 
Glad I came to visit – your iOS update comment is well-founded…
thanks a lot. good to hear that. i hope it get’s fixed soon.