Electrical Dash Lines
A proper schematic for LVDT's looks as follows

The common phases are noted by the position of the dots.


Excitation of sine is on single top "primary" coil in all cases and position is detected by ratio of coupling to differential output "secondary" coils with BLU/GRN usually joined into 1 wire. 

When centered, they will have equal amplitude and opposite polarity because one secondary is wound in the opposite direction, so that signal is inverted compared to primary.

Dotted lines make no sense electrically for sensors ( no pun intended ) but for optional grounding depending on winding layers for optimal protection from EMI such as lightning, perhaps dotted line shows optional connection for ground connection as an EMI shield.