Phil,
Those are how the signals are operated. This track is bi-directional. So each block has two posts. One that claims the block when you hit it, this is located at the very start of the block, then the second block located at the very end of it is what clears it. They have been playing with train detection, but it really has not worked too well. Also train detection would make it hard to run double sections. The manually triggered signals work really well. Also there are a few switches that are remotely operated via similar looking posts.
Here is a link to the track plan : http://www.sn3.org/eprr/track/track...master-plan.gif

- Andrew