On 14 June, 16:35, Paul Corfield wrote:
On Sun, 14 Jun 2009 16:29:37 +0100, "Graham Harrison"

wrote:
Waiting for a North London train a couple of days ago the station person
(what are they called these days?) came down onto the platform carrying what
looked like a mobile phone. * He went behind the side of the shelter and
appeared to hold the "mobile phone" to the fence (the fence was creosoted a
very dark colour). * He appeared to do the same thing in more than one place
on both platforms. * When I looked there was a black "stud" (only word I can
think of) which was simply inserted into the fence panel - it wasn't a
fastener, there was not a post or anything behind the panel.

Is there any significance to his actions?

The "studs" are almost certainly a location identifier that the hand
held unit will read. By holding the unit against the stud it shows he
has been to the area as part of a planned inspection. Bar codes can also
be used. I have seen building security staff use this system to prove
they've undertaken their rounds. *LUL is trialling something similar to
be able to record the fact that hourly security checks around the
station have been completed.

--
Paul C

In olden times, there were mechanical versions of this system, where
staff had to punch a small card or similar actin to show they had done
their rounds. The machines were known as 'tell tales'.