<s>
JPL	B-Protocol
sequences	I-Protocol
or	O
JPL	B-Protocol
codes	I-Protocol
consist	O
of	O
two	O
linear	B-Architecture
feedback	I-Architecture
shift	I-Architecture
registers	I-Architecture
(	O
LFSRs	B-Architecture
)	O
whose	O
code	O
sequence	O
lengths	O
La	O
and	O
Lb	O
must	O
be	O
prime	O
(	O
relatively	O
prime	O
)	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
for	O
more	O
than	O
two	O
LFSRs	B-Architecture
to	O
be	O
interconnected	O
through	O
multiple	O
XORs	B-Application
at	O
the	O
output	O
for	O
as	O
long	O
as	O
all	O
code	O
sequence	O
lengths	O
of	O
the	O
individual	O
LFSR	B-Architecture
are	O
relatively	O
prime	O
to	O
one	O
another	O
.	O
</s>
<s>
JPL	B-Protocol
sequences	I-Protocol
were	O
originally	O
developed	O
in	O
the	O
Jet	O
Propulsion	O
Labs	O
,	O
from	O
which	O
the	O
name	O
for	O
these	O
code	O
sequences	O
is	O
derived	O
.	O
</s>
<s>
Areas	O
of	O
application	O
include	O
distance	O
measurements	O
utilizing	O
spread	B-Architecture
spectrum	I-Architecture
signals	O
for	O
satellites	O
and	O
in	O
space	O
technology	O
.	O
</s>
<s>
Their	O
major	O
advantage	O
is	O
,	O
that	O
they	O
produce	O
relatively	O
long	O
sequences	O
with	O
only	O
two	O
LFSRs	B-Architecture
,	O
which	O
makes	O
it	O
energy	O
efficient	O
and	O
very	O
hard	O
to	O
detect	O
due	O
to	O
huge	O
spreading	O
factor	O
.	O
</s>
