Graham Harrison wrote:
I took the Overground from Clapham Junction to West Brompton yesterday.
All the written signage included Imperial Wharf but I'm pretty certain
that when the train was announced Imperial Wharf was omitted. Now, I
may be wrong and I wasn't going to wait another 30 minutes to find out
but it set me wondering, how is the digital announcement updated? How
much extra recording is required for "Imperial Wharf"? Just 2 words or
more? Then how is the update distributed? Is there a central server
and a comms line or does someone send out a disc? Are Dave and Doris
on a permanent contract to come and make updates, how often?

I don't know the answer, but can report experience with changes over
the past few years at Stevenage. At least one of them demonstrates that
it isn't just about having the right words in the system.

When initially installed, Dave did the up platforms and Doris did the
down. This worked very well - simultaneous announcements on both platforms
were easy to distinguish because the voices had very different pitches.
At some point, Doris began to lose the odd word. The most striking was
'4', but only when used as a platform number. She could say "4" as part
of a time, but when a train was due to pass platform 4 it came out as
"platform silent gap". After a week or two of this, Doris became Dave.

Two Dave's wasn't so good, because they often spoke together. Some time
later, they both became Doris. And then "GNER" became "National Express
East Coast". Neither Doris nor Dave knew how to say this, so for
some months we would have "Platform 2 for the silent gap service to
London Kings Cross" and the like. I think they learned how to say it
just in time to have to forget it and learn how to say "East Coast."

Similarly, when WAGN was replaced by First Capital Connect, Doris said
the new name in a voice which was distinctly different, and never sounded
right. Eventually, this was fixed but it took over a year.