ator receives a call for some line on a
non-adjacent position, having answered this call with her answering
plug, she inserts the calling plug into the jack of one of these
transfer lines that leads to the proper other section. The operator at
that section is notified either verbally or by signal, and she completes
the connection between the other end of the transfer line and the line
of the called subscriber; the connection between the two subscribers
thus being effected through the cords of the two operators in question
linked together by the transfer line. Such a transfer line as just
described, requiring the connection at each of its ends by one of the
plugs of the operator's cord pair, is termed a _jack-ended trunk_ or a
_jack-ended transfer line_ because each of its ends terminates in a
jack.

[Illustration: Fig. 330. Jack-Ended Transfer Circuit]

There is another method of accomplishing the same general result by the
employment of the so-called _plug-ended trunk_ or _plug-ended transfer
line_. In this the trunk or transfer line terminates at one end, the
answering end, in a jack as before, and the connection is made with it
by the answering operator by means of the calling plug of the pair with
which she answered the originating call. The other end of this trunk,
instead of terminating in a jack, ends in a plug and the second operator
involved in the connection, after being notified, picks up this plug and
inserts it in the jack of the called subscriber, thus completing the
connection without employing one of her regular cord pairs.

_Jack-Ended Trunk._ In Fig. 330 are shown the circuits of a commonly
employed jack-ended trunk for transfer boards. The talking circuit, as
usual, is shown in heavy lines and terminates in the tip and sleeve of
the transfer jacks at each end. The auxiliary contacts in these jacks
and the circuits connecting them are absolutely independent of the
talking circuit and are for the purpose of signaling only, the
arrangement of the jacks being such that when a plug is inserted, the
spring _1_ will break from spring _2_ and make with spring _3_.
Obviously, the insertion of a plug in either of the jacks will establish
such connections as to light both lamps, since the engagement of spring
_1_ with spring _3_ in either of the jacks will connect both of the
lamps in multiple across the battery, this connection including always
the contacts _1_ and _2_ of the other jack. From this it follows