[MrFixr55]

For Phone connections, one pin jack connects to B+ and also to the screen. This supplies B+ to the headphone. The other pin connects the phone to the detector plate through the feedback coil. In other words, plate, feedback coil and phones are all in series and connected to B+.
I'm with Chaz on what the other connection to the antenna coil is, it's ground or to a counterpoise.