CAB SIGNALS IN GENERAL.                 589

this difficulty still further plainly follows from what is said
below concerning audible cab signals.
 No principle involved in the whole art of railway signalling
is more important than that all errors of indication must be
"on the side of safety, not on the side of danger." One may
well question whether such a thing as a fixed audible signal
which obeys this exceedingly important rule is a physical
possibility.  Without digressing to discuss this interest-
ing proposition, it can at least be said that, at all events,
such a fixed audible signal has never been produced. Since
the Dammond system produces an audible cab signal that
conforms to this requirement with the practical perfection,
hitherto attained only by automatic fixed visual signals, the
actual fact is that the cab signals now afford the only audi-
ble indications that accord with sound signal engineering
principles.
  It is a signalling truism to assert that a fireman cannot
see any fixed signals he passes while engaged at any one of
several important duties which together consume a very
large part of his running time, and it is equally evident that
he can instantly, unerringly, and without the slightest possi-
ble difficulty, "read" an audible cab signal, no matter what
he may be doing nor where he may be looking when such a
signal is sounded.
  Unlike any cab system, a fixed block signalling system,
even if perfectly satisfactory as to economy and even if it
operated with absolute infallibility would still be a HIGHLY
OBJECTIONABLE system, because even such a fixed sys-
tem would still be open to the objection of giving its indica-
tions where their user never is. An infallibly operating
fixed block signalling system is one which does the right
thing at the right time in the wrong place.
        AUTOMATIC THREE-INDICATION CAB SIGNALS.
  Realizing the marked superiority of automatic over man-
ual block systems, whether fixed or cab, for routes over
which traffic is at all dense, the inventor has been especially




			

OHS/National Afro-American Museum & Cultural Center Serial Collection

African Methodist Episcopal Church Review, Vol. 28, Num. 2

Volume:  28
Issue Number:  02
Date:  10/1911