which an
almost uninformed operator could sit and operate it at once. It is not
difficult to lay out a scheme of labels which will enable such a board
to be operated without any detailed instructions being given.

=Desirable Features.= The board should contain means of connecting
certain of the local private exchange lines to the central-office trunks
when the board is unattended. Also, it is desirable that it should
contain means whereby any local private exchange line may be connected
to the trunk so that its station will act as an ordinary subscriber's
station. Whether the trunks of the private exchange lead to a manual or
an automatic equipment, it often is desired to connect a local line
through in that way, either so that the calling person may make his
calls without the knowledge of the private exchange operator, because he
wishes to make a large number of calls in succession, or because for
some other reason he prefers to transact his business directly with or
through the exchange than to entrust it to his operator.

CHAPTER XXXV

INTERCOMMUNICATING SYSTEMS

=Definition.= The term "intercommunicating" has been given to a
specialized type of telephone system wherein the line belonging to each
station is extended to each of the other stations, resulting in all
lines extending to all stations. Each station is provided with apparatus
by means of which the telephone user there may connect his own telephone
with the line of the station with which he wishes to communicate,
enabling him to signal and talk with the person at that station.

=Limitations.= The idea is simple. Each person does his own switching
directly, and no operator is required. It is easy to see, however, that
the system has limitations. The amount of line wire necessary in order
to run each line to each station is relatively great, and becomes
prohibitive except in exchanges involving a very small number of
subscribers, none of which is remote from the others. Again, the amount
of switching apparatus required becomes prohibitive for any but a small
number of stations. As a result, twenty-five or thirty stations are
considered the usual practical limit for intercommunicating systems.

=Types.= An intercommunicating system may be either magneto or
common-battery, according to whether it uses magneto or common-battery
telephones. The former is the simpler; the latter is the more generally
used.

[Illustration: WESTERN ELECTRIC COMPANY BA