-relay armature, due to the breaking of the relay circuit at the
jack contacts. The subscriber then receives current for his transmitter
through the cord-circuit battery connections. The supervisory relay
connected with the answering cord is not lighted, because, although the
lamp-circuit connection is completed at the jack, the supervisory relay
is operated to hold the lamp circuit open. Conversation ensues between
the operator and the subscriber, after which the operator tests the line
called for with the tip of the calling plug of the pair used in
answering. If the called line is not busy, no click will ensue, because
both the tested ring and the calling plug are at the same potential.
Finding no click, the operator will insert the plug and ring by means of
the ringing key. When the operator plugs in, the supervisory lamp,
associated with the calling plug, becomes lighted because the circuit is
completed at the jack and the supervisory relay remains de-energized,
since the line circuit is open at the subscriber's station. When the
called subscriber responds, the calling supervisory lamp goes out
because of the energization of the supervisory relay. Both lamps remain
out during the conversation, but when either subscriber hangs up, the
corresponding supervisory lamp will be lighted because of the falling
back of the supervisory relay armature.

If the called line is busy, a click will be heard, for the reason
described, and the operator will so inform the calling subscriber. It
goes without saying, that in any multiple-switchboard system a plug may
be found in the actual multiple jack that is reached for, in which case,
although no test will be made, the busy condition will be reported back
to the calling subscriber.

_Economy._ It has been the belief of the Western Electric engineers that
a real economy is accomplished in this type of board by the saving in
relay equipment. It is, of course, apparent at a glance that with a
switchboard long enough and of sections enough, the cost of extra jack
springs and their platinum contacts must become great enough to offset
the saving accomplished by omitting the cut-off relay. This makes it
apparent that if there is any economy in this type of multiple
switchboard, it must be found in the very small boards where there are
but few jacks per line and where the extra cost of the cut-off jack is
not enough to offset the extra cost of an added relay. It is the growing
belief, howe