raffic during the busiest time of day and not the number of lines
that determine the size of a multiple switchboard so far as its length
is concerned. The number of lines determines the size of the multiple in
any one section, but it is the amount of traffic, the number of calls
that are made in the busiest period, that determines the number of
operators required, and thus the number of positions. Had this now very
obvious fact been more fully realized in the past, some companies would
be operating at less expense, and some manufacturers would have sold
less expensive switchboards.

The whole question as to the number of positions boils down to how many
answering jacks and line signals may be placed at each operator's
position without overburdening the operator with incoming traffic at the
busy time of day. Obviously, some lines will call more frequently than
others, and hence the proper number of answering jacks at the different
positions will vary. Obviously, also, due to changes in the personnel of
the subscribers, the rates of calling of different groups of lines will
change from time to time, and this may necessitate a regrouping of the
line signals and answering jacks on the positions; and changes in the
personnel of the operators or in their skill also demand such
regrouping.

_Intermediate Frame._ The intermediate distributing frame is provided
for this purpose, and will be more fully discussed in subsequent
chapters. Suffice it to say here that the intermediate distributing
frame permits the answering jacks and line signals to be shifted about
among the operators' positions, so that each position will have just
enough originating traffic to keep each of the operators economically
busy during the busiest time of the day.

CHAPTER XXV

THE MAGNETO MULTIPLE SWITCHBOARD

=Field of Utility.= The principles of the multiple switchboard set forth
in the last chapter were all developed long before the common-battery
system came into existence, and consequently all of the first multiple
switchboards were of the magneto type. Although once very widely used,
the magneto multiple switchboard has almost passed out of existence,
since it has become almost universal practice to equip exchanges large
enough to employ multiple boards with common-battery systems.
Nevertheless there is a field for magneto multiple switchboards, and in
this field it has recently been coming into increasing favor. In those
towns equipp