parts of a simple
common-battery switchboard deserves some attention. The form of the
switchboard need not differ essentially from that employed in magneto
work, but ordinarily the cabinet is somewhat smaller on account of the
smaller amount of room required by its lamps and jacks. An excellent
idea of the line jacks and lamps, plugs, keys, and supervisory signals
may be obtained from Fig. 327, which is a detail view taken from a
Kellogg board. In the vertical panel of the board above the plug shelf
are arranged the line jacks and the lamps in rows of twenty each, each
lamp being immediately beneath its corresponding jack. Such jacks are
ordinarily mounted on 1/2-inch centers both vertically and horizontally,
so that a group of one hundred lamps and line jacks will occupy a space
only slightly over 10 by 5 inches. Such economy of space is not required
in the simple magneto board, because the space might easily be made
larger without in any way taxing the reach of the operator. The reason
for this comparatively close mounting is a result, not of the
requirements of the simple non-multiple common-battery board itself, but
of the fact that the jack strips and lamp strips, which are required in
very large numbers in multiple boards, have to be mounted extremely
close together, and as the same lamp strips and jack strips are often
available for simple switchboards, an economy in manufacture is effected
by adherence to the same general dimensions.

[Illustration: Fig. 328. Simple Common-Battery Switchboard with
Removable Relay Panel]

A rear view of a common form of switchboard cabinet, known as the
_upright type_ and manufactured by the Dean Company, is shown in Fig.
328. In this all the relays are mounted on a hinged rack, which, when
opened out as indicated, exposes the wiring to view for inspection or
repairs. Access to both sides of the relays is thus given to the
repairman who may do all his work from the rear of the board without
disturbing the operator.

Fig. 329 shows a three-position cabinet of Kellogg manufacture, this
being about the limit in size of boards that could properly be called
simple. Obviously, where a switchboard cabinet must be made of greater
length than this, _i. e._, than is required to accommodate three
operators, it becomes too long for the operators to reach all over it
without undue effort or without moving from their seats. The so-called
_transfer board_ and the _multiple board_ (to be con