Multiple Arc Box.
A resistance box arranged so that the coils may be plugged in multiple
instead of in series. Such can be used as a rheostat, as the resistance
can be very gradually changed by putting the coils one by one into
parallel with each other. Thus by adding in parallel with a 10 ohm coil
a 10,000 ohm coil the resistance is decreased to 9.999001 ohms, and thus
the resistance can be very slowly changed without sudden stops or abrupt
changes.
[Transcriber's note: The correct value is 9.99001]
Multiple Series.
Arrangements of electric apparatus in a circuit in a number of series,
which minor series are then arranged in parallel. The term may be used
as a noun, as "arranged in multiple-series," or as an adjective, as "a
multiple-series circuit."
Fig. 248. MULTIPLE SERIES CONNECTION.
Multiple Switch Board.
A switch board on whose face connecting spring jacks or other devices
are repeated for the same circuits, so that different operators have
each the entire set of connections repeated on the section of the board
immediately in front of and within their reach. This multiplication of
the same set of connections, giving one complete set to each operator,
gives the title "multiple" to the type of switch board in question. The
typical multiple switch board used in telephone exchanges is the best
example of this construction. The calling annunciators of the
subscribers are distributed along the bottom of the board extending its
full length. To each operator a given number is assigned, all within
reach of the right or left hand. This gives five or six feet length of
board to each, and an operator only responds to those subscribers within
his range. But anyone of his subscribers may want to connect with any of
the others in the entire central station. Accordingly in front of each
operator spring jacks are arranged, one for each of the entire set of
subscribers connected in that office. The operator connects as required
any of the calling subscribers, who are comparatively few, to any one of
the large number served by the central station. Thus the entire set of
subscribers' spring jacks are multiplied over and over again so as to
give one set to each operator.