the plug of the incoming trunk into the multiple
jack of the subscriber's line, and remains illuminated until the
subscriber has answered. This is accomplished in the following manner:
when the operator plugs into the jack of the line called, relay _5_ is
energized but is immediately de-energized by the disconnecting of the
circuit of this relay from the sleeve conductor of the cord when the
ringing key is depressed, the selection of the ringing key being
determined by the particular party on the line desired. These ringing
keys have associated with them a set of springs _9_, which springs are
operated when any one of the ringing keys is depressed. Thus, with a
ringing key depressed and the relay _5_ de-energized, the ringing lamp
will be illuminated by means of a circuit as follows: from the live side
of the battery, through the ringing lamp _12_, through the back contact
and armature of the relay _6_, through the armature and contact of relay
_4_, then through the armature and front contact of relay _2_--which at
this time is the relay bridged across the trunk and, therefore,
energized--and thence through the back contact and armature of relay
_5_ to ground. When the subscriber removes his receiver from the hook,
the relay _1_ will become energized as previously described, and will,
therefore, operate relay _6_ to break the circuit of the ringing lamp.
The circuit thus established by the operation of relay _1_ is as
follows: from the live side of battery, through the winding of relay
_6_, through the armature and contact of relay _1_, through the armature
and contact of relay _4_, through the armature and front contact of
relay _2_, thence through the armature and back contact of relay _5_ to
ground. As soon as the _B_-operator notes that the ringing lamp has gone
out, she knows that no further ringing is required on that line, thus
allowing the operation of relay _5_ and accomplishing the locking out of
the ringing lamp during the remainder of that connection. The relay _6_,
after having once pulled up, remains locked up through the rear contact
of the left-hand armature of relay _5_ and ground, until the plug is
removed from the jack.

At the end of the conversation, when the _A_-operator has disconnected
her cord circuit on the illumination of the supervisory signals, both
relays _2_ and _4_ will be in an unoperated condition and will provide a
circuit for illuminating the disconnect lamp associated with the
_B_-op