of
operators who must work before it. It is mechanically possible to make a
switchboard for ten thousand lines only 15 feet long, seating seven
operators. The entire multiple of ten thousand lines could appear three
times in such a switchboard. The seven operators could not handle the
traffic we know would be originated by ten thousand lines, with any
present system of charging for service. Even a rough knowledge of the
probable traffic would enable us to approximate the number of operators
needed and to equip each position, not only with access to the ten
thousand lines to be called, but also with just enough keyboard
equipment, serving as tools, and just enough answering jacks, serving as
means of bringing the traffic to her. It is foreknowledge of traffic
which enables a switchboard to fit the task it is to perform.

=Rates of Calling.= The rates of calling of different kinds of lines
vary. The lines of business stations originate more calls than do the
lines of residences. Some kinds of business originate more calls than
others. Some kinds of business have a higher rate of calling in one
season than in others. Flat-rate lines originate more calls than do
message-rate lines. When a line changes from a flat rate to a message
rate, the number of originating calls per day decreases. An operator's
position, handling message-rate lines only, can serve more lines than if
all of them were at flat rates. The number of message-rate or
coin-prepayment lines which an operator's position can care for depends
not only on the traffic but on the method of charging for service,
whether by tickets or meters and upon the kind of meters; or it depends
on the method of collecting the coins. In some regions, the rate of
calling, on the introduction of a complete measured-service plan, has
been reduced to one-fourth of what it was on the flat-rate plan.

In manual switchboards of early types, wherein the position of the
subscriber's answering jack was fixed by his telephone number, the
inequality of traffic became a serious problem. Most of the subscribers
who first installed telephones when the exchange was small, retained
their telephones and numbers; as their use of the telephone grew with
their business, it was customary to find the positions answering the
lower numbers much more busy than the positions answering the higher
numbers, the latter belonging to later and usually less active business
places.

_Functions of Intermediate