ver, among engineers, that the multiple switchboard must be
very small indeed in order that the added complexity of the cut-off
jacks and wiring may be able to save anything over the two-relay type of
line; and it is believed that where economy is necessary in small
boards, it may be best effected by employing cheaper and more compact
forms of relays and mounting them, if necessary, directly in the
switchboard cabinet.

NOTE. These two standard types of common-battery multiple
switchboards of the Western Electric Company represent the
development through long years of careful work on the part of
the Western Electric and Bell engineers, credit being
particularly due to Scribner, McBerty, and McQuarrie of the
Western Electric Company, and Hayes of the American Telephone
and Telegraph Company.

=Kellogg Two-Wire Multiple Board.= The simplicity in the jacks permitted
by the use of the cut-off relay in the Western Electric common-battery
multiple switchboard for larger exchanges was carried a step further by
Dunbar and Miller in the development of the so-called two-wire
common-battery multiple switchboard, which for many years has been the
standard of the Kellogg Switchboard and Supply Company. The particular
condition which led to the development of the two-wire system was the
demand at that time on the Kellogg Company for certain very large
multiple switchboards, involving as many as 18,000 lines in the
multiple. Obviously, this necessitated a small jack, and obviously a
jack having only two contacts, a tip spring and a sleeve, could be made
more easily and with greater durability of this very small size than a
jack requiring three or more contacts. Other reasons that were
considered were, of course, cheapness in cost of construction and
extreme simplicity, which, other things being equal, lends itself to low
cost of maintenance.

_Line Circuit._ Like the standard Western Electric board for large
offices, the Kellogg two-wire board employs two relays for each line,
the line relay under the control of the subscriber and in turn
controlling the lamp, and a cut-off relay under the control of the
operator and in turn controlling the connection of the line relay with
the line. The line circuit as originally developed and as widely used by
the Kellogg Company is shown in Fig. 350. The extreme simplicity of the
jacks is apparent, as is also the fact that but two wires lead through
the multip