rivate-line test board is shown a
four-position wire chief's desk, upon which are provided facilities for
making all of the tests inside and outside.

[Illustration: Fig. 430. Line-Switch Units]

[Illustration: Fig. 431. Automatic Apparatus at Lansing Office]

The main frame is shown at the right of Fig. 428, just to the right of a
gallery from which a step-ladder leads. The left-hand side of this frame
is the line or protector side, but the portion toward the observer in
this picture is unequipped. These equipped protector strips carry 400
pairs of terminals each, and the consequent length of these strips makes
necessary the gallery shown, in order that all of them may be readily
accessible.

[Illustration: Fig. 432. Main Distributing Frame, Lansing Office]

[Illustration: Fig. 433. Line Switches]

[Illustration: POWER PLANT FOR AUTOMATIC SWITCHBOARD EQUIPMENT Bay
Cities Home Telephone Company, Berkeley, Cal.]

[Illustration: Fig. 434. Secondary Line Switches and First Selectors]

=Automatic Offices.= There is no great difference in the amount of floor
space required in central offices employing automatic and manual
equipment. Whatever difference there is, is likely to be in favor of the
automatic. The fact that no such rigid requirement exists in the
arrangement of automatic apparatus, as that which makes it necessary to
place the sections of a multiple board all in one row, makes it possible
to utilize the available space more economically with automatic than
with manual equipment.

[Illustration: Fig. 435. Second Selectors]

[Illustration: Fig. 436. Toll Distributing Frame and Harmonic
Converters]

In manual practice it is necessary to place the distributing frames and
power apparatus in a separate room from that containing the switchboard,
but in an automatic exchange no such necessity exists; in fact, so far
as the distributing-frame equipment is concerned, it is considered
desirable to have it located in the same room as the automatic switches.

The battery room in an automatic exchange should be entirely separate
from the operating room, since the fumes from the battery would be fatal
to the proper working of the automatic switches.

_Typical Automatic Office._ The floor-plan and views of a medium-sized
automatic office at Lansing, Michigan, have been chosen as representing
typical practice. The floor plan is shown in Fig. 429. The apparatus
indicated in full lines represents the present equipment