<s>
Mouse	B-General_Concept
Sonar	I-General_Concept
is	O
a	O
computer	O
accessibility	O
feature	O
available	O
in	O
Microsoft	B-Application
Windows	I-Application
versions	O
since	O
Windows	B-Device
ME	I-Device
.	O
</s>
<s>
When	O
Mouse	B-General_Concept
Sonar	I-General_Concept
is	O
enabled	O
,	O
releasing	O
the	O
Ctrl	B-Device
key	I-Device
causes	O
several	O
concentric	O
circles	O
to	O
appear	O
around	O
the	O
pointer	O
for	O
a	O
short	O
time	O
.	O
</s>
<s>
The	O
Mouse	B-General_Concept
Sonar	I-General_Concept
feature	O
is	O
disabled	O
by	O
default	B-General_Concept
,	O
and	O
it	O
may	O
be	O
turned	O
on	O
using	O
the	O
Mouse	O
Control	O
Panel	O
applet	O
(	O
details	O
may	O
vary	O
with	O
different	O
Windows	O
versions	O
)	O
.	O
</s>
<s>
Programmatically	O
,	O
the	O
Mouse	B-General_Concept
Sonar	I-General_Concept
state	O
may	O
be	O
accessed	O
with	O
the	O
SystemParametersInfo	O
Windows	B-Library
API	I-Library
function	O
in	O
conjunction	O
with	O
the	O
symbolic	O
value	O
SPI_GETMOUSESONAR	O
(=	O
0x101C	O
,	O
used	O
to	O
retrieve	O
state	O
information	O
)	O
or	O
SPI_SETMOUSESONAR	O
(=	O
0x101D	O
,	O
used	O
to	O
enable	O
or	O
disable	O
the	O
feature	O
)	O
for	O
the	O
first	O
function	O
parameter	O
,	O
defined	O
in	O
most	O
newer	O
Windows	O
header	O
files	O
.	O
</s>
