or less remote, and they are commonly termed _local_ toll and
_long-distance_ toll lines according to the degree of remoteness. A
toll line, whether local or long-distance, may be looked upon in the
nature of an inter-exchange trunk.

Districts. The district in a given community which is served by a
single central office is called an office district. Likewise, the
district which is served by a complete exchange is called an exchange
district. An exchange district may, therefore, consist of a number of
central-office districts, just as an exchange may comprise a number of
central offices. To illustrate, the entire area served by the exchange
of the Chicago Telephone Company in Chicago, embracing the entire city
and some of its suburbs, is the Chicago exchange district. The area
served by one of the central offices, such as the Hyde Park office,
the Oakland office, the Harrison office, or any of the others, is an
office district.

Switchboards. The apparatus at the central office by which the
telephone lines are connected for conversation and afterwards
disconnected, and by which the various other functions necessary to
the giving of complete telephone service are performed, is called a
switchboard. This may be simple in the case of small exchanges, or of
vast complexity in the case of the larger exchanges.

Sometimes the switchboards are of such nature as to require the
presence of operators, usually girls, to connect and disconnect the
line and perform the other necessary functions, and such switchboards,
whether large or small, are termed _manual_.

Sometimes the switchboards are of such a nature as not to require the
presence of operators, the various functions of connection,
disconnection, and signaling being performed by the aid of special
forms of apparatus which are under the control of the subscriber who
makes the call. Such switchboards are termed _automatic_.

Of recent years there has appeared another class of switchboards,
employing in some measure the features of the automatic and in some
measure those of the manual switchboard. These boards are commonly
referred to as _semi-automatic_ switchboards, presumably because they
are supposed to be half automatic and half manual.

_Manual_. Manual switchboards may be subdivided into two classes
according to the method of distributing energy for talking purposes.
Thus we may have _magneto_ switchboards, which are those capable of
serving lines equipped with