many operators must be employed as there
are hundreds of subscribers whose lines are served in a switchboard, and
this means that in an exchange of 5,000 subscribers, 50 operators'
positions would be required, or 16-2/3 sections. Each of these sections
would be equipped with the full 5,000 jacks, so that each operator could
have a connection terminal for each line.

_The Multiple._ These groups of 5,000 jacks, repeated on each of the
sections are termed multiple jacks, and the entire equipment of these
multiple jacks and their wiring is referred to as the multiple. It will
be shown presently that the multiple jacks are only used for enabling
the operator to connect with the called subscriber. In other words these
jacks are for the purpose of enabling each operator to have within her
reach any line that may be called for regardless of what line originates
the call. We will now consider what arrangements are provided for
enabling the operator to receive the signal indicating a call and what
provisions are made for her to answer the call in response to such a
signal.

=Line Signals.= Obviously it is not necessary to have the line signals
repeated on each section of the board as are the multiple jacks. If a
line has one definite place on the switchboard where its signal may be
received and its call may be answered, that suffices. Each line,
therefore, in addition to having its multiple jacks distributed one on
each section of the switchboard, has a line signal and an individual
jack immediately associated with it, located on one only of the
sections. This signal usually is in the form of a lamp and is termed the
line signal, and this jack is termed the answering jack since it is by
means of it that the operator always answers a call in response to the
line signal.

_Distribution of Line Signals._ It is evident that it would not do to
have all of these line signals and answering jacks located at one
section of the board for then they would not be available to all of the
operators. They are, therefore, distributed along the board in such a
way that one group of them will be available to one operator, another
group to another operator, and so on; the number of answering jacks and
signals in any one group being so proportioned with respect to the
number of calls that come in over them during the busy hour that it will
afford just about enough calls to keep the operator at that position
busy.

We may summarize these condit