ibed herein, may
be used. The problem becomes a special one, however, when communication
must also be had with the subscribers of a public exchange, since then
trunking is involved in which the conditions differ materially from
those encountered in trunking between the several offices in a
multi-office exchange.

For such communication one or more trunk lines are led from the private
branch office usually to the nearest central office of the public
exchange and such trunks are called private branch-exchange trunks. They
are the paths for communication between the private exchange and the
public exchange. For establishing the connections either between the
local lines themselves or between the local lines and the trunks, and
for performing other duties that will be referred to, one or more
private branch-exchange operators are employed at the switchboard of the
private establishment.

The private branch exchange may operate in conjunction with a manual or
an automatic public exchange, but whether manual or automatic, the
private exchange is usually manually operated, although it is quite
possible to make a private branch exchange that is wholly automatic and
will, therefore, involve no operator at all.

=Functions of the Private Branch-Exchange Operator.= It is possible, as
just stated, entirely to dispense with the private branch-exchange
operator so far as the mere connection and disconnection of the lines is
concerned. But the real function of the private branch-exchange operator
is a broader one than this and it is for this reason that even in
connection with automatic public exchanges, operators are desirable at
the private branches. The private branch-exchange operator is, as it
were, the doorkeeper of the telephone entrance to the private
establishment. She is the person first met by the public in entering
this telephone door. There is the same reason, therefore, why she should
be intelligent, courteous, and obliging as that the ordinary doorkeeper
should possess these characteristics.

As to incoming traffic to a private branch exchange, an intelligent
operator may do much toward directing the calls to the proper department
or person, even though the person calling may have little idea as to
whom he desires to reach. This saves the time of the person who makes
the call as well as that of the people at the private branch stations,
since it prevents their being unnecessarily called.

The functions of the priv