In the accompanying sketches are shown one of the few sets of German recognition
signals that have fallen into American hands. There are two sheets of these
instructions (1) the aircraft signals, which are changed daily; (2) signals
subject to infrequent change. Unfortunately, it is not possible to reproduce
the colors in which the originals were printed.
a. Signals Changed Daily -- Air Corps
These are shown in figure 1. This sheet is kept posted in the sentry post. The
word Muster (sample) printed across the face indicates that this
particular sheet was not used for actual operation -- it may have been for
instruction only as is also suggested by the tack-heads indicated in the
corners of the inner outlines.
While accurate knowledge of its use is not obtainable, it seems probable
that the star, blinker, colored light, and emergency signals illustrated
might be customarily given by airplanes. However, the red star rocket may
well be sent up by ground troops as a challenge, in which case an approaching
plane would reply in either the same manner or by one of the other
signals, blinker or light.
ES-1 in figure 2 may be interpreted as a challenge to an approaching
unit -- air, ground or afloat. The one white rocket is equivalent
to, "Halt -- who's there?" The approacher replies with one white and
three red -- the identification signal meaning, "Friend," and the
challenger replies with two white rockets, "Pass friend." The interpretation of the
other signals 2 to 7 are simple, the acknowledgement, ES, meaning, "Signal received."