COAST ARTILLERY, JOURNAL - Air Defense Artillery

MORTARFIRE CONTROL 507
repeating back the azimuth to the plotting room as a check when it is
late in getting to the pits.
g. Spotting Device.- Various devices were used during the tests.
Any spotting device that meets the requirements of Coast Artillery
Board Project No. 416 (See COASTARTILLERYJOURNALfor January,
1926) will be satisfactory.
h. Impact Board (now known as the Adjustment Chart) .-Both the
impact board described in T. R. 435-221 and the Modified Impact Board
(See COASTARTILLERYJOURNALfor April, 1926) have been used during
the tests. The Modified Impact Board was more satisfactory than
the Impact Board.
i. Mechanical Display Board.-This is a device which can be
operated mechanically from the plotting room to display data in both
pits and has been installed at Battery Anderson for many years. It is
realized that not all mortar batteries are equipped with mechanical
transmission, but wherever such display boards can be installed, provision
for the installation is desirable and should be carried into effect.
The board should not be confused with the special display board used
in this development, which is of an entirely different type. The combined
use of both display boards was a feature of the development and
was most satisfactory since the combination afforded a suitable check
back on the firing data while permitting the necessary interpolations.
j. The time-interval system was altered to ring as indicated in
Paragraph 7.
k. A change was made in the' telephone communications between
the plotting room and the pits. Two men operated the special display
board in the pits. Each operator wore a headset. One was connected
to that operator on the deflection board in the plotting room who performed
interpolation in azimuth. The other was connected to that
operator on the percentage corrector who performed interpolation in
elevation. These communications functioned satisfactorily.
9. The following fire control equipment was in the pits:
a. A display board connected directly with the mechanical transmission
device in the plotting room as mentioned in paragraph 8 i,
above.
b. A special display hoard on which all data were posted. This
functioned satisfactorily throughout (See Fig. 1). Attention is invited
to Paragraph 8 k, above, and to Paragraph 10, below.
10. The special display board (Figure 1) was simple and inexpensive.
It was made of heavy rough lumber procured locally. A
heavy double-faced blackboard was mounted in the frame as 5ho'l>>1.
The operators stood in rear of the board, recorded the data telephoned
to them from the plotting room and turned the board to the pits every