Most stations do not have signals within them, confining
them to positions just before and just after the platform. Of the stations
that do have them over the platform, like 14th Street and 7th Avenue above,
most will be arranged like this, suspended horizontally from the ceiling
under the platform lights. Note that signals underground do not, as a rule,
have hoods over the targets.
Here is a standard signal mounted on the local tracks
of the same station. Because of it's position between the third rail and
the wall, the relay box beneath the head has been relocated elsewhere, most
likely the wall-mounted box behind it. These signals are a little more
commonplace than those mounted on the ceiling. Two-track island platforms
are more likely to have signals at mid-platform, and if they precede a junction
or interlocking, they're guaranteed to have some.