<s>
[ [ 	O
File:The	O
Royal	O
Navy	O
during	O
the	O
Second	O
World	O
War	O
A3651.jpg	O
|thumbnail|right|Mark	O
IV	O
Directors	O
on	O
HMS	O
King	O
George	O
V	O
.	O
The	O
large	O
rectangular	O
box	O
centred	O
above	O
the	O
director	O
contains	O
the	O
gyro	B-Device
rate	I-Device
unit	I-Device
.	O
</s>
<s>
The	O
Mk	O
IV	O
director	O
was	O
a	O
considerable	O
improvement	O
and	O
used	O
gyroscopes	B-Application
in	O
a	O
gyro	B-Device
rate	I-Device
unit	I-Device
coupled	O
to	O
an	O
optical	O
rangefinder	O
and	O
Type	O
282	O
radar	O
to	O
determine	O
the	O
range	O
,	O
speed	O
and	O
direction	O
of	O
enemy	O
aircraft	O
and	O
then	O
used	O
an	O
on-director	B-Device
computer	I-Device
to	O
produce	O
an	O
accurate	O
fire	O
control	O
solution	O
to	O
hit	O
the	O
target	O
.	O
</s>
<s>
Later	O
versions	O
of	O
the	O
Mk	O
IV	O
director	O
introduced	O
remote	O
power	O
control	O
(	O
RPC	O
)	O
and	O
could	O
control	O
the	O
gun	O
mounting	O
by	O
remote	O
control	O
from	O
the	O
director.Campbell	O
,	O
Naval	O
Weapons	O
of	O
World	O
War	O
Two	O
,	O
p20	O
The	O
Mk	O
IV	O
director	O
was	O
fully	O
tachymetric	B-Device
,	O
but	O
performance	O
suffered	O
as	O
the	O
director	O
was	O
not	O
stabilized	O
against	O
the	O
movement	O
of	O
the	O
ship	O
.	O
</s>
<s>
Campbell	O
notes	O
that	O
the	O
first	O
USN	O
tachymetric	B-Device
40mm	O
gun	O
directors	O
did	O
not	O
appear	O
until	O
1942	O
,	O
while	O
neither	O
the	O
Italian	O
,	O
German	O
nor	O
the	O
Japanese	O
navy	O
had	O
comparable	O
close	O
range	O
AA	O
directors	O
.	O
</s>
<s>
The	O
Pom-Pom	B-Device
Director	I-Device
,	O
Mark	O
IV	O
in	O
The	O
Gunnery	O
Pocket	O
Book''	O
,	O
B.R.	O
</s>
