<s>
In	O
telecommunication	O
and	O
signal	O
processing	O
,	O
companding	B-Algorithm
(	O
occasionally	O
called	O
compansion	B-Algorithm
)	O
is	O
a	O
method	O
of	O
mitigating	O
the	O
detrimental	O
effects	O
of	O
a	O
channel	O
with	O
limited	O
dynamic	O
range	O
.	O
</s>
<s>
The	O
name	O
is	O
a	O
portmanteau	O
of	O
the	O
words	O
compressing	O
and	O
expanding	O
,	O
which	O
are	O
the	O
functions	O
of	O
a	O
compander	B-Algorithm
at	O
the	O
transmitting	O
and	O
receiving	O
ends	O
,	O
respectively	O
.	O
</s>
<s>
The	O
use	O
of	O
companding	B-Algorithm
allows	O
signals	O
with	O
a	O
large	O
dynamic	O
range	O
to	O
be	O
transmitted	O
over	O
facilities	O
that	O
have	O
a	O
smaller	O
dynamic	O
range	O
capability	O
.	O
</s>
<s>
Companding	B-Algorithm
is	O
employed	O
in	O
telephony	O
and	O
other	O
audio	O
applications	O
such	O
as	O
professional	O
wireless	B-Device
microphones	I-Device
and	O
analog	O
recording	O
.	O
</s>
<s>
The	O
electronic	O
circuit	O
that	O
does	O
this	O
is	O
called	O
a	O
compander	B-Algorithm
and	O
works	O
by	O
compressing	O
or	O
expanding	O
the	O
dynamic	O
range	O
of	O
an	O
analog	O
electronic	O
signal	O
such	O
as	O
sound	O
recorded	O
by	O
a	O
microphone	O
.	O
</s>
<s>
Companded	B-Algorithm
quantization	O
is	O
the	O
combination	O
of	O
three	O
functional	O
building	O
blocks	O
–	O
namely	O
,	O
a	O
(	O
continuous-domain	O
)	O
signal	O
dynamic	O
range	O
compressor	O
,	O
a	O
limited-range	O
uniform	O
quantizer	O
,	O
and	O
a	O
(	O
continuous-domain	O
)	O
signal	O
dynamic	O
range	O
expander	O
that	O
inverts	O
the	O
compressor	O
function	O
.	O
</s>
<s>
In	O
practice	O
,	O
companders	B-Algorithm
are	O
designed	O
to	O
operate	O
according	O
to	O
relatively	O
simple	O
dynamic	O
range	O
compressor	O
functions	O
that	O
are	O
designed	O
to	O
be	O
suitable	O
for	O
implementation	O
using	O
simple	O
analog	O
electronic	O
circuits	O
.	O
</s>
<s>
The	O
two	O
most	O
popular	O
compander	B-Algorithm
functions	O
used	O
for	O
telecommunications	O
are	O
the	O
A-law	B-Algorithm
and	O
μ-law	B-Algorithm
functions	O
.	O
</s>
<s>
Companding	B-Algorithm
is	O
used	O
in	O
digital	O
telephony	O
systems	O
,	O
compressing	O
before	O
input	O
to	O
an	O
analog-to-digital	O
converter	O
,	O
and	O
then	O
expanding	O
after	O
a	O
digital-to-analog	O
converter	O
.	O
</s>
<s>
This	O
is	O
equivalent	O
to	O
using	O
a	O
non-linear	O
ADC	O
as	O
in	O
a	O
T-carrier	O
telephone	O
system	O
that	O
implements	O
A-law	B-Algorithm
or	O
μ-law	B-Algorithm
companding	B-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
a	O
linearly	O
encoded	O
16-bit	O
PCM	B-Algorithm
signal	O
can	O
be	O
converted	O
to	O
an	O
8-bit	O
WAV	O
or	O
AU	O
file	O
while	O
maintaining	O
a	O
decent	O
SNR	O
by	O
compressing	O
before	O
the	O
transition	O
to	O
8-bit	O
and	O
expanding	O
after	O
conversion	O
back	O
to	O
16-bit	O
.	O
</s>
<s>
Professional	O
wireless	B-Device
microphones	I-Device
do	O
this	O
since	O
the	O
dynamic	O
range	O
of	O
the	O
microphone	O
audio	O
signal	O
itself	O
is	O
larger	O
than	O
the	O
dynamic	O
range	O
provided	O
by	O
radio	O
transmission	O
.	O
</s>
<s>
Companding	B-Algorithm
also	O
reduces	O
the	O
noise	O
and	O
crosstalk	O
levels	O
at	O
the	O
receiver	O
.	O
</s>
<s>
Companders	B-Algorithm
are	O
used	O
in	O
concert	O
audio	O
systems	O
and	O
in	O
some	O
noise	O
reduction	O
schemes	O
.	O
</s>
<s>
The	O
use	O
of	O
companding	B-Algorithm
in	O
an	O
analog	O
picture	O
transmission	O
system	O
was	O
patented	O
by	O
A	O
.	O
</s>
<s>
In	O
1942	O
,	O
Clark	O
and	O
his	O
team	O
completed	O
the	O
SIGSALY	O
secure	O
voice	O
transmission	O
system	O
that	O
included	O
the	O
first	O
use	O
of	O
companding	B-Algorithm
in	O
a	O
PCM	B-Algorithm
(	O
digital	O
)	O
system	O
.	O
</s>
<s>
In	O
1953	O
,	O
B	O
.	O
Smith	O
showed	O
that	O
a	O
nonlinear	O
DAC	O
could	O
be	O
complemented	O
by	O
the	O
inverse	O
nonlinearity	O
in	O
a	O
successive-approximation	O
ADC	O
configuration	O
,	O
simplifying	O
the	O
design	O
of	O
digital	O
companding	B-Algorithm
systems	O
.	O
</s>
<s>
In	O
1970	O
,	O
H	O
.	O
Kaneko	O
developed	O
the	O
uniform	O
description	O
of	O
segment	O
(	O
piecewise	O
linear	O
)	O
companding	B-Algorithm
laws	O
that	O
had	O
by	O
then	O
been	O
adopted	O
in	O
digital	O
telephony	O
.	O
</s>
<s>
In	O
the	O
1980s	O
(	O
and	O
'	O
90s	O
)	O
,	O
many	O
of	O
the	O
music	O
equipment	O
manufacturers	O
(	O
Roland	O
,	O
Yamaha	O
,	O
Korg	O
)	O
used	O
companding	B-Algorithm
when	O
compressing	O
the	O
library	O
waveform	O
data	O
in	O
their	O
digital	O
synthesizers	O
.	O
</s>
<s>
Unfortunately	O
exact	O
algorithms	O
are	O
not	O
known	O
,	O
neither	O
if	O
any	O
of	O
the	O
manufacturers	O
ever	O
used	O
the	O
Companding	B-Algorithm
scheme	O
which	O
is	O
described	O
in	O
this	O
article	O
.	O
</s>
<s>
The	O
only	O
known	O
thing	O
is	O
that	O
manufacturers	O
did	O
use	O
data	O
compression	O
in	O
the	O
mentioned	O
time	O
period	O
and	O
that	O
some	O
people	O
refer	O
to	O
it	O
as	O
"	O
companding	B-Algorithm
"	O
while	O
in	O
reality	O
it	O
might	O
mean	O
something	O
else	O
,	O
for	O
example	O
data	O
compression	O
and	O
expansion	O
.	O
</s>
<s>
24	O
MB	O
of	O
physical	O
waveform	O
ROM	O
in	O
a	O
Korg	B-Device
Trinity	I-Device
is	O
actually	O
48	O
MB	O
when	O
uncompressed	O
.	O
</s>
