In the system shown in the illustration, the station at section I is unable to signal any other station nor is any other station able to signal the station in section I. The station can, however, ring itself by proper positioning of its selector switch. EL-0093 A. The selector switch is grounded at the problem station diverting current from the other stations' ringing devices. B. There is an open between terminal 'C' of the problem station and the multi-conductor cable to the other stations. C. The contacts to the left of component 'B' are stuck closed allowing only a single station to respond to itself. D. The switch at component 'C' is stuck open.