<s>
RONJA	B-Protocol
(	O
Reasonable	B-Protocol
Optical	I-Protocol
Near	I-Protocol
Joint	I-Protocol
Access	I-Protocol
)	O
is	O
a	O
free-space	O
optical	O
communication	O
system	O
originating	O
in	O
the	O
Czech	O
Republic	O
,	O
developed	O
by	O
Karel	O
Kulhavý	O
of	O
Twibright	O
Labs	O
and	O
released	O
in	O
2001	O
.	O
</s>
<s>
Ronja	B-Protocol
can	O
be	O
used	O
to	O
create	O
a	O
10	O
Mbit/s	O
full	O
duplex	O
Ethernet	O
point-to-point	O
link	O
.	O
</s>
<s>
Two	O
coaxial	O
cables	O
are	O
used	O
to	O
connect	O
the	O
rooftop	O
installation	O
with	O
a	O
protocol	O
translator	O
installed	O
in	O
the	O
house	O
near	O
a	O
computer	O
or	O
switch	B-Protocol
.	O
</s>
<s>
Building	O
instructions	O
,	O
blueprints	O
,	O
and	O
schematics	O
are	O
published	O
under	O
the	O
GNU	B-Application
Free	I-Application
Documentation	I-Application
Licence	I-Application
.	O
</s>
<s>
Only	O
free	B-Application
software	I-Application
tools	O
are	O
used	O
in	O
the	O
development	O
.	O
</s>
<s>
Ronja	B-Protocol
is	O
a	O
project	O
of	O
Twibright	O
Labs	O
.	O
</s>
<s>
Ronja	B-Protocol
Tetrapolis	O
:	O
Range	O
of	O
,	O
red	O
visible	O
light	O
.	O
</s>
<s>
Connect	O
with	O
8P8C	O
connector	O
into	O
a	O
network	B-Protocol
card	I-Protocol
or	O
switch	B-Protocol
.	O
</s>
<s>
Ronja	B-Protocol
10M	O
Metropolis	O
:	O
Range	O
of	O
,	O
red	O
visible	O
light	O
.	O
</s>
<s>
Connects	O
to	O
Attachment	B-Protocol
Unit	I-Protocol
Interface	I-Protocol
.	O
</s>
<s>
Ronja	B-Protocol
Inferno	O
:	O
Range	O
of	O
,	O
invisible	O
infrared	O
light	O
.	O
</s>
<s>
Ronja	B-Protocol
Lopipe	O
:	O
The	O
original	O
(	O
discontinued	O
)	O
design	O
using	O
red	O
visible	O
light	O
and	O
a	O
RS232	O
interface	O
for	O
a	O
max	O
115	O
kbit/s	O
PPP/SLIP	O
link	O
.	O
</s>
<s>
By	O
definition	O
,	O
clear	O
visibility	B-Application
between	O
the	O
transmitter	O
and	O
receiver	O
is	O
essential	O
.	O
</s>
<s>
It	O
requires	O
an	O
ability	O
to	O
set	O
full	O
duplex	O
manually	O
on	O
the	O
network	B-Protocol
card	I-Protocol
or	O
switch	B-Protocol
to	O
take	O
advantage	O
of	O
full	O
duplex	O
,	O
since	O
it	O
does	O
n't	O
support	O
autonegotiation	B-Protocol
.	O
</s>
<s>
Must	O
be	O
plugged	O
directly	O
into	O
PC	O
or	O
switch	B-Protocol
using	O
the	O
integral	O
Ethernet	O
cable	O
.	O
</s>
<s>
A	O
complete	O
RONJA	B-Protocol
system	O
is	O
made	O
up	O
of	O
2	O
transceivers	O
:	O
2	O
optical	O
transmitters	O
and	O
2	O
optical	O
receivers	O
.	O
</s>
<s>
The	O
complete	O
system	O
layout	O
is	O
shown	O
in	O
the	O
block	B-Application
diagram	I-Application
.	O
</s>
<s>
A	O
transimpedance	O
amplifier	O
is	O
a	O
very	O
sensitive	O
broadband	B-General_Concept
high-speed	O
device	O
featuring	O
a	O
feedback	O
loop	O
.	O
</s>
<s>
Ronja	B-Protocol
however	O
uses	O
a	O
feedbackless	O
design	O
where	O
the	O
PIN	O
has	O
a	O
high	O
working	O
electrical	O
resistance	O
(	O
100	O
kilohms	O
)	O
which	O
together	O
with	O
the	O
total	O
input	O
capacitance	O
(	O
roughly	O
8	O
pF	O
,	O
5	O
pF	O
PIN	O
and	O
3	O
pF	O
input	O
MOSFET	B-Architecture
cascode	O
)	O
makes	O
the	O
device	O
operate	O
with	O
a	O
passband	B-Algorithm
on	O
a	O
6dB/oct	O
slope	O
of	O
low	O
pass	O
formed	O
by	O
PIN	O
working	O
resistance	O
and	O
total	O
input	O
capacitance	O
.	O
</s>
<s>
It	O
has	O
a	O
bandwidth	B-Algorithm
of	O
9MHz	O
,	O
where	O
10	O
Mbit/s	O
Manchester-modulated	O
systems	O
need	O
bandwidth	B-Algorithm
of	O
around	O
16MHz	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
nominally	O
digital	O
74AC04	O
is	O
operating	O
as	O
a	O
structured	O
power	O
CMOS	B-Device
switch	B-Protocol
completely	O
in	O
analog	O
mode	O
.	O
</s>
<s>
This	O
way	O
the	O
LED	O
junction	O
is	O
flooded	O
and	O
cleared	O
of	O
carriers	O
as	O
quickly	O
as	O
possible	O
,	O
basically	O
by	O
short	B-Application
circuit	I-Application
discharge	O
.	O
</s>
<s>
2	O
)	O
A	O
blocking	O
ceramic	O
capacitor	O
bank	O
backing	O
up	O
the	O
74AC04	O
switching	O
array	O
is	O
crucial	O
for	O
correct	O
operation	O
,	O
because	O
charging	O
and	O
discharging	O
the	O
LED	O
is	O
done	O
by	O
short	B-Application
circuit	I-Application
.	O
</s>
<s>
Ronja	B-Protocol
Twister	O
is	O
an	O
electronic	O
interface	O
for	O
free	O
space	O
optical	O
datalink	O
based	O
on	O
counter	O
and	O
shift	O
register	O
chips	O
.	O
</s>
<s>
It	O
is	O
a	O
part	O
of	O
the	O
Ronja	B-Protocol
design	O
.	O
</s>
<s>
Soderberg	O
,	O
studying	O
Ronja	B-Protocol
sociologically	O
,	O
writes	O
:	O
"	O
Arguably	O
,	O
the	O
first	O
project	O
that	O
vindicated	O
the	O
methods	O
and	O
licensing	O
schemes	O
of	O
free	B-Application
software	I-Application
development	I-Application
,	O
applied	O
those	O
practices	O
to	O
open	O
hardware	O
development	O
,	O
and	O
pulled	O
off	O
a	O
state-of-the-art	O
technology	O
without	O
any	O
backing	O
from	O
universities	O
or	O
firms	O
,	O
was	O
the	O
Ronja	B-Protocol
project.	O
"	O
</s>
<s>
The	O
whole	O
toolchain	B-General_Concept
is	O
built	O
strictly	O
upon	O
free	O
tools	O
and	O
the	O
source	O
files	O
are	O
provided	O
,	O
free	O
,	O
under	O
the	O
GPL	B-License
.	O
</s>
<s>
Such	O
costs	O
normally	O
can	O
include	O
software	B-License
licence	I-License
costs	O
,	O
time	O
investment	O
into	O
resolution	O
of	O
compatibility	O
issues	O
between	O
proprietary	O
applications	O
,	O
or	O
costs	O
of	O
intellectual	O
property	O
licence	O
negotiations	O
.	O
</s>
<s>
The	O
decision	O
to	O
conceive	O
the	O
project	O
this	O
way	O
was	O
inspired	O
by	O
observed	O
organizational	O
efficiency	O
of	O
Free	B-Application
Software	I-Application
.	O
</s>
<s>
On	O
Christmas	O
2001	O
,	O
Ronja	B-Protocol
became	O
the	O
world	O
's	O
first	O
10	O
Mbit/s	O
Free	O
Space	O
Optics	O
device	O
with	O
free	B-Application
sources	I-Application
.	O
</s>
