[NSW] "knob things" on platforms.. what the heck do they do???

["Mitch" <webmaster@mitch.zzn.com>]

I have observed at many stations round knobs.. What do they do?

They're about one foot in diameter, they're either made of metal or wood and
they have 4 screws in them. What do they do? Are they outlets for where
Telstra are supposed to put their phones?

ASCII REPRESENTATION:

                 ###################
             ###########################
           ###### $ ############# $ ######
           ###############################
           ###############################
           ###############################
           ###### $ ############# $ ######
             ###########################
                 ###################

where the $ is a screw. Sorry for the terrible drawing, but it might help
explain it!