he
battery feed wires being shown at the left.

=Supervision of Private Branch Connections.= At the main office where
common-battery equipment is used, the private branch trunks terminate
before the _A_-operators exactly in the same way as ordinary
subscribers' lines, _i. e._, each in an answering jack and lamp at one
position and in a multiple jack on each section. It goes without saying,
therefore, that the handling of a private branch call, either incoming
or outgoing, should be done by the _A_-operator in the same manner as a
call on an ordinary subscriber's line, and that the supervision of the
connection should impose no special duties on the _A_-operator.

There has been much discussion, and no final agreement, as to the proper
method of controlling the supervisory lamp at the main office of a cord
that is, at the time, connected to a private branch trunk. Three general
methods have been practiced:

The first method is to have the private branch subscriber directly
control the supervisory lamp at the main office without producing any
effect upon the private branch supervisory signal; this latter signal
being displayed only after the connection has been taken down at the
main office and in response to the withdrawal of the main office plug
from the private branch jack. This is good practice so far as the
main-office discipline is concerned but it results in a considerable
disadvantage to both the city and private branch subscribers in that it
is impossible for the private branch subscriber, when connected to the
other, to re-signal the private branch operator without the connection
being first taken down.

The second method is to have the private branch subscriber control both
the supervisory signal at the private branch board and at the main
board. This has the disadvantage of bringing both operators in on the
circuit when the private branch subscriber signals.

The third method, and one that seems best, is to place the supervisory
lamp of the private branch board alone under the control of the private
branch subscriber, so that he may attract the attention of the private
branch operator without disturbing the supervisory signal at the main
office. The supervisory signal at the main office in this case is
displayed only when the private branch operator takes down the
connection. This practice results in a method of operation at the main
office that involves no special action on the part of the _A_-operator.