<s>
The	O
Kerrison	B-Device
Predictor	I-Device
was	O
one	O
of	O
the	O
first	O
fully	O
automated	O
anti-aircraft	B-Application
fire-control	B-Application
systems	I-Application
.	O
</s>
<s>
Such	O
devices	O
had	O
been	O
used	O
on	O
ships	O
for	O
gunnery	O
control	O
for	O
some	O
time	O
,	O
and	O
versions	O
such	O
as	O
the	O
Vickers	B-Device
Predictor	I-Device
were	O
available	O
for	O
larger	O
anti-aircraft	B-Application
guns	O
intended	O
to	O
be	O
used	O
against	O
high-altitude	O
bombers	O
.	O
</s>
<s>
The	O
British	O
Army	O
's	O
new	O
Bofors	O
40	O
mm	O
guns	O
were	O
intended	O
as	O
their	O
standard	O
low-altitude	O
anti-aircraft	B-Application
weapons	O
.	O
</s>
<s>
Making	O
matters	O
worse	O
was	O
that	O
these	O
ranges	O
were	O
exactly	O
where	O
the	O
Luftwaffes	O
dive	B-Application
bombers	I-Application
,	O
which	O
were	O
quickly	O
proving	O
to	O
be	O
a	O
decisive	O
weapon	O
in	O
the	O
Blitzkrieg	B-Language
,	O
were	O
attacking	O
from	O
.	O
</s>
<s>
His	O
solution	O
was	O
a	O
calculator	O
that	O
dispensed	O
with	O
many	O
of	O
the	O
corrections	O
and	O
timing	O
issues	O
seen	O
in	O
devices	O
like	O
the	O
Vickers	B-Device
Predictor	I-Device
which	O
were	O
intended	O
for	O
high-altitude	O
fire	O
.	O
</s>
<s>
Key	O
to	O
the	O
concept	O
was	O
the	O
use	O
of	O
two	O
ball-and-disk	B-Device
integrators	I-Device
,	O
used	O
in	O
this	O
case	O
to	O
maintain	O
a	O
constant	O
rate	O
of	O
motion	O
.	O
</s>
<s>
The	O
Kerrison	B-Device
predictor	I-Device
did	O
not	O
calculate	O
fuse	O
settings	O
,	O
as	O
the	O
shells	O
fired	O
by	O
the	O
40mm	O
Bofors	O
gun	O
,	O
with	O
which	O
it	O
was	O
designed	O
to	O
work	O
,	O
were	O
contact-fused	O
.	O
</s>
<s>
The	O
Predictor	O
proved	O
to	O
be	O
able	O
to	O
hit	O
practically	O
anything	O
that	O
flew	O
in	O
a	O
straight	O
line	O
,	O
and	O
it	O
was	O
particularly	O
effective	O
against	O
dive	B-Application
bombers	I-Application
.	O
</s>
<s>
The	O
No.7	O
anti-aircraft	B-Application
composite	O
predictor	O
,	O
also	O
designed	O
by	O
Kerrison	O
was	O
similar	O
in	O
some	O
ways	O
.	O
</s>
<s>
Although	O
it	O
was	O
more	O
accurate	O
than	O
the	O
Kerrison	B-Device
predictor	I-Device
,	O
Sperry	O
was	O
unable	O
to	O
keep	O
up	O
with	O
production	O
of	O
its	O
more	O
expensive	O
and	O
complex	O
M-7	O
director	O
.	O
</s>
<s>
In	O
September	O
1940	O
,	O
General	O
George	O
C	O
.	O
Marshall	O
asked	O
the	O
British	O
for	O
the	O
loan	O
of	O
four	O
Bofors	O
40mm	O
guns	O
with	O
Kerrison	B-Device
Predictors	I-Device
for	O
testing	O
.	O
</s>
<s>
During	O
testing	O
the	O
Kerrison	B-Device
Predictor	I-Device
provided	O
accurate	O
fire	O
control	O
to	O
a	O
range	O
in	O
excess	O
of	O
,	O
and	O
the	O
Bofors	O
gun	O
was	O
reliable	O
.	O
</s>
<s>
In	O
the	O
fall	O
of	O
1940	O
,	O
the	O
Ordnance	O
Department	O
standardized	O
the	O
Kerrison	B-Device
Predictor	I-Device
for	O
use	O
with	O
their	O
37mm	O
gun	O
.	O
</s>
<s>
With	O
aircraft	O
speeds	O
increasing	O
dramatically	O
during	O
the	O
war	O
,	O
even	O
the	O
speed	O
of	O
the	O
Kerrison	B-Device
Predictor	I-Device
proved	O
lacking	O
by	O
the	O
end	O
.	O
</s>
<s>
After	O
a	O
month	O
of	O
limited	O
success	O
against	O
them	O
,	O
every	O
available	O
anti-aircraft	B-Application
gun	O
was	O
moved	O
to	O
the	O
strip	O
of	O
land	O
on	O
the	O
approach	O
to	O
London	O
,	O
and	O
the	O
new	O
sights	O
proved	O
to	O
be	O
more	O
than	O
capable	O
against	O
them	O
.	O
</s>
