row of keys, including what is called a _starting key_ and also
keys for making the party-line selection.

[Illustration: Fig. 407. Strip of Selecting Keys]

[Illustration: Fig. 408. Wiring of Key Shelf]

The simplicity of the operator's key equipment is one of its attractive
features. Fig. 408 shows one of the key shelves opened so as to expose
to view all of the apparatus and wiring that is placed before the
operator. The reason for providing more than one key set on each
operator's position is, that after a call has been set up on one key
set, a few seconds is required before the automatic apparatus controlled
by the key set can do its work and release the key set ready for another
call. The provision of more than one key set makes it possible for the
operator to start setting up another call on another key set without
waiting for the first to be released by the automatic apparatus.

[Illustration: Fig. 409. Switch Room of Automanual Central Office]

=Automatic Switching Equipment.= A general view of the arrangement of
automatic switches in an exchange established by the North Electric
Company at Ashtabula, Ohio, is shown in Fig. 409. The desk in the
foreground is that of the wire chief. This automatic apparatus consists
largely of relays and automatic selecting switches. The switches are of
the step-by-step type, having vertical and rotary movements, and an idea
of one of them, minus its contact banks, is given in Fig. 410. The
control of the automatic switches by the operator's key sets is through
the medium of a power-driven, impulse-sending machine. From this machine
impulses are taken corresponding to the numbers of the keys depressed.

[Illustration: Fig. 410. Selecting Switch]

=Automatic Distribution of Calls.= A feature of great interest in this
system is the manner in which the incoming calls are distributed among
the operators. From each key set an operator's trunk is extended to what
is called a secondary selector switch, through which it may be connected
to a primary selector trunk and calling line. When a subscriber calls by
taking down his receiver, his line relay pulls up and causes a primary
selector switch to connect his line with an idle local trunk or link
circuit, at the same time starting up a secondary selector switch which
immediately connects the primary trunk and the calling line to an
operator's idle key set. If an operator is at the time engaged in
setting up a call on a key set, or