<s>
A	O
tachymetric	B-Device
anti-aircraft	I-Device
fire	I-Device
control	I-Device
system	I-Device
generates	O
target	O
position	O
,	O
speed	O
,	O
direction	O
,	O
and	O
rate	O
of	O
target	O
range	O
change	O
,	O
by	O
computing	O
these	O
parameters	O
directly	O
from	O
measured	O
data	O
.	O
</s>
<s>
The	O
term	O
tachymetric	B-Device
should	O
more	O
properly	O
be	O
spelled	O
as	O
"	O
tachometric	O
"	O
which	O
comes	O
from	O
the	O
Greek	O
"	O
takhos	O
"	O
=	O
speed	O
,	O
and	O
"	O
metric	O
"	O
=	O
measure	O
,	O
hence	O
tachometric	O
,	O
to	O
measure	O
speed	O
.	O
</s>
<s>
An	O
alternative	O
,	O
non-tachometric	O
,	O
gonometric	B-Device
method	O
of	O
AA	O
prediction	O
is	O
for	O
specially	O
trained	O
observers	O
to	O
estimate	O
the	O
course	O
and	O
speed	O
of	O
the	O
target	O
manually	O
and	O
feed	O
these	O
estimates	O
,	O
along	O
with	O
the	O
measured	O
bearing	O
and	O
range	O
data	O
,	O
into	O
the	O
AA	O
fire	B-Application
control	I-Application
computer	I-Application
which	O
then	O
generates	O
change	O
of	O
bearing	O
rate	O
and	O
change	O
of	O
range	O
data	O
,	O
and	O
passes	O
them	O
back	O
to	O
the	O
observer	O
,	O
typically	O
by	O
a	O
"	O
follow	O
the	O
pointer	O
"	O
,	O
indicator	O
of	O
predicted	O
target	O
elevation	O
and	O
bearing	O
or	O
by	O
remote	O
power	O
control	O
of	O
the	O
observer	O
's	O
optical	O
instruments	O
.	O
</s>
<s>
An	O
example	O
of	O
tachometric	O
AA	O
fire	O
control	O
would	O
be	O
the	O
USN	O
Mk	B-Application
37	I-Application
system	I-Application
.	O
</s>
<s>
The	O
early	O
RN	O
High	B-Device
Angle	I-Device
Control	I-Device
System	I-Device
(	O
HACS	B-Device
)	O
I	O
through	O
IV	O
and	O
the	O
early	O
Fuze	B-Device
Keeping	I-Device
Clock	I-Device
(	O
FKC	O
)	O
were	O
examples	O
of	O
non-tachometric	O
systems	O
.	O
</s>
<s>
By	O
1940	O
the	O
RN	O
was	O
adding	O
a	O
Gyro	B-Device
Rate	I-Device
Unit	I-Device
(	O
GRU	O
)	O
which	O
fed	O
bearing	O
and	O
elevation	O
data	O
to	O
a	O
Gyro	B-Device
Rate	I-Device
Unit	I-Device
Box	O
computer	O
(	O
GRUB	O
)	O
,	O
which	O
also	O
received	O
ranging	O
data	O
to	O
calculate	O
target	O
speed	O
and	O
direction	O
directly	O
,	O
and	O
this	O
tachometric	O
data	O
was	O
then	O
fed	O
directly	O
to	O
the	O
HACS	B-Device
fire	B-Application
control	I-Application
computer	I-Application
,	O
converting	O
the	O
HACS	B-Device
into	O
a	O
tachometric	O
system	O
.	O
</s>
