s
digit of the number being called, and the resulting movement of the
central-office apparatus will continue the calling subscriber's line
through a trunk to a piece of apparatus capable of further extending his
line toward the line terminals of the thousand subscribers whose numbers
begin with the digit chosen. The next movement of the dial corresponding
to the hundreds digit of the called number will operate this piece of
apparatus to again extend the calling subscriber's line through another
trunk to apparatus representing the particular hundred in which the
called subscriber's number is. The third movement of the dial
corresponding to the tens digit will pick out the group of ten
containing the called subscriber's line, and the fourth movement
corresponding to the units digit will pick out and connect with the
particular line called.

_Lorimer System._ In the Lorimer automatic system invented by the
Lorimer Brothers, and now being manufactured by the Canadian Machine
Telephone Company of Toronto, Canada, the subscriber sets up the number
he desires complete by moving four levers on his telephone so that the
desired number appears visibly before him. He then turns a handle and
the central-office apparatus, under the control of the electrical
conditions thus set up by the subscriber, establishes the connection. In
this system, unlike the Strowger system, the controlling impulses are
not caused by the movement of the subscriber's apparatus in returning to
its normal position after being set by the subscriber. Instead, the
conditions established at the subscriber's station by the subscriber in
setting up the desired number, merely determine the point in the series
of impulses corresponding to each digit at which the stepping impulses
local to the central office shall cease, and in this way the proper
number of impulses in the series corresponding to each digit is
determined.

_Magnet- vs. Power-Driven Switches._ These two systems differ radically
in another respect. In the Strowger system it is the electrical impulses
initiated at the subscriber's apparatus that actually cause the movement
of the switching parts at the central office, these impulses energizing
electromagnets which move the central-office switching devices a step at
a time the desired number of steps. In the Lorimer system the switches
are all power-driven and the impulses under the control of the
subscriber's instrument merely serve to control the app