his chapter that as
each section accommodated three operators, the total number of sections
in a switchboard will be at least one-third the total number of required
operators. This thought needs further development, for to stop at that
statement is to arrive somewhat short of the truth. In order to do this
it is necessary to consider the field in the multiple, reached by each
operator. The section is of such size, or should be, that an operator
seated in the center position of it may, without undue effort, reach all
over the multiple. But the operator at the right-hand position cannot
reach the extreme left portion of the multiple of that section, nor can
the operator at the left reach the extreme right. How then may each
operator reach a jack for every line? Remembering that the multiple
jacks are arranged exactly the same in each section, each jack always
occupying the same relative position, it is easy to see that while the
operator at a right-hand position of a section cannot reach the
left-hand third of the multiple in her own section, she may reach the
left-hand third of the multiple in the section at her right, and this,
together with the center and right-hand thirds of her own section,
represents the entire number of lines. So it is with the left-hand
operator at any section, she reaches two-thirds of all the lines in the
multiple of her own section and one-third in that of the section at her
left.

_End Positions._ This makes it necessary to inquire about the operators
at the end positions of the entire board. To provide for these the
multiple is extended one-third of a section beyond them, so as to supply
at the ends of the switchboard jacks for those lines which the end
operators cannot reach on their own sections. Sometimes instead of
adding these end sections to the multiple for the end operators, the
same result is accomplished by using only the full and regular sections
of the multiple, and leaving the end positions without operators'
equipment, as well as without answering jacks, line signals, and cords
and plugs, so that in reality the end operator is at the middle position
of the end section. This, in our opinion, is the better practice, since
it leaves the sections standard, and makes it easier to extend the
switchboard in length, as it grows, by the mere addition of new sections
without disturbing any of the old multiple.

=Influence of Traffic.= We wish again to emphasize the fact that it is
the t