<s>
A	O
synchro	B-Algorithm
(	O
also	O
known	O
as	O
selsyn	B-Algorithm
and	O
by	O
other	O
brand	O
names	O
)	O
is	O
,	O
in	O
effect	O
,	O
a	O
transformer	B-Algorithm
whose	O
primary-to-secondary	O
coupling	O
may	O
be	O
varied	O
by	O
physically	O
changing	O
the	O
relative	O
orientation	O
of	O
the	O
two	O
windings	O
.	O
</s>
<s>
The	O
primary	O
winding	O
of	O
the	O
transformer	B-Algorithm
,	O
fixed	O
to	O
the	O
rotor	O
,	O
is	O
excited	O
by	O
an	O
alternating	O
current	O
,	O
which	O
by	O
electromagnetic	O
induction	O
,	O
causes	O
voltages	O
to	O
appear	O
between	O
the	O
Y-connected	O
secondary	O
windings	O
fixed	O
at	O
120	O
degrees	O
to	O
each	O
other	O
on	O
the	O
stator	O
.	O
</s>
<s>
Synchro	B-Algorithm
systems	O
were	O
first	O
used	O
in	O
the	O
control	O
system	O
of	O
the	O
Panama	O
Canal	O
in	O
the	O
early	O
1900s	O
to	O
transmit	O
lock	O
gate	O
and	O
valve	O
stem	O
positions	O
,	O
and	O
water	O
levels	O
,	O
to	O
the	O
control	O
desks	O
.	O
</s>
<s>
Fire-control	B-Application
system	I-Application
designs	O
developed	O
during	O
World	O
War	O
II	O
used	O
synchros	O
extensively	O
,	O
to	O
transmit	O
angular	O
information	O
from	O
guns	O
and	O
sights	O
to	O
an	O
analog	O
fire	B-Application
control	I-Application
computer	I-Application
,	O
and	O
to	O
transmit	O
the	O
desired	O
gun	O
position	O
back	O
to	O
the	O
gun	O
location	O
.	O
</s>
<s>
Early	O
systems	O
just	O
moved	O
indicator	O
dials	O
,	O
but	O
with	O
the	O
advent	O
of	O
the	O
amplidyne	O
,	O
as	O
well	O
as	O
motor-driven	O
high-powered	O
hydraulic	O
servos	O
,	O
the	O
fire	B-Application
control	I-Application
system	I-Application
could	O
directly	O
control	O
the	O
positions	O
of	O
heavy	O
guns	O
.	O
</s>
<s>
Digital	O
devices	O
such	O
as	O
the	O
rotary	B-Algorithm
encoder	I-Algorithm
have	O
replaced	O
synchros	O
in	O
most	O
other	O
applications	O
.	O
</s>
<s>
Selsyn	B-Algorithm
motors	O
were	O
widely	O
used	O
in	O
motion	O
picture	O
equipment	O
to	O
synchronize	O
movie	B-Application
cameras	I-Application
and	O
sound	O
recording	O
equipment	O
,	O
before	O
the	O
advent	O
of	O
crystal	O
oscillators	O
and	O
microelectronics	O
.	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
synchro	B-Algorithm
systems	O
:	O
torque	O
systems	O
and	O
control	O
systems	O
.	O
</s>
<s>
In	O
a	O
torque	O
system	O
,	O
a	O
synchro	B-Algorithm
will	O
provide	O
a	O
low-power	O
mechanical	O
output	O
sufficient	O
to	O
position	O
an	O
indicating	O
device	O
,	O
actuate	O
a	O
sensitive	O
switch	O
or	O
move	O
light	O
loads	O
without	O
power	O
amplification	O
.	O
</s>
<s>
In	O
simpler	O
terms	O
,	O
a	O
torque	O
synchro	B-Algorithm
system	O
is	O
a	O
system	O
in	O
which	O
the	O
transmitted	O
signal	O
does	O
the	O
usable	O
work	O
.	O
</s>
<s>
In	O
a	O
control	O
system	O
,	O
a	O
synchro	B-Algorithm
will	O
provide	O
a	O
voltage	O
for	O
conversion	O
to	O
torque	O
through	O
an	O
amplifier	O
and	O
a	O
servomotor	B-Algorithm
.	O
</s>
<s>
In	O
simpler	O
terms	O
,	O
a	O
control	O
synchro	B-Algorithm
system	O
is	O
a	O
system	O
in	O
which	O
the	O
transmitted	O
signal	O
controls	O
a	O
source	O
of	O
power	O
which	O
does	O
the	O
usable	O
work	O
.	O
</s>
<s>
A	O
synchro	B-Algorithm
will	O
fall	O
into	O
one	O
of	O
eight	O
functional	O
categories	O
:	O
</s>
<s>
Output	O
:	O
electrical	O
output	O
same	O
as	O
TX	O
but	O
supplied	O
to	O
a	O
control	O
transformer	B-Algorithm
or	O
control	O
differential	O
transmitter	O
.	O
</s>
<s>
Output	O
:	O
same	O
as	O
TDX	O
but	O
supplied	O
to	O
only	O
a	O
control	O
transformer	B-Algorithm
or	O
another	O
CDX	O
.	O
</s>
<s>
A	O
synchro	B-Algorithm
transmitter	I-Algorithm
's	O
shaft	O
is	O
rotated	O
by	O
the	O
mechanism	O
that	O
sends	O
information	O
,	O
while	O
the	O
synchro	B-Algorithm
receiver	I-Algorithm
's	O
shaft	O
rotates	O
a	O
dial	O
,	O
or	O
operates	O
a	O
light	O
mechanical	O
load	O
.	O
</s>
<s>
Synchro	B-Algorithm
transmitters	I-Algorithm
and	O
receivers	O
must	O
be	O
powered	O
by	O
the	O
same	O
branch	O
circuit	O
,	O
so	O
to	O
speak	O
;	O
the	O
mains	O
excitation	O
voltage	O
sources	O
must	O
match	O
in	O
voltage	O
and	O
phase	O
.	O
</s>
<s>
Different	O
makes	O
of	O
selsyns	B-Algorithm
,	O
used	O
in	O
interlock	O
systems	O
,	O
have	O
different	O
output	O
voltages	O
.	O
</s>
<s>
Synchro	B-Algorithm
transmitters	I-Algorithm
are	O
as	O
described	O
,	O
but	O
50	O
-	O
and	O
60-Hz	O
synchro	B-Algorithm
receivers	I-Algorithm
require	O
rotary	O
dampers	O
to	O
keep	O
their	O
shafts	O
from	O
oscillating	O
when	O
not	O
loaded	O
(	O
as	O
with	O
dials	O
)	O
or	O
lightly	O
loaded	O
in	O
high-accuracy	O
applications	O
.	O
</s>
<s>
A	O
different	O
type	O
of	O
receiver	O
,	O
called	O
a	O
control	O
transformer	B-Algorithm
(	O
CT	O
)	O
,	O
is	O
part	O
of	O
a	O
position	O
servo	O
that	O
includes	O
a	O
servo	O
amplifier	O
and	O
servo	B-Algorithm
motor	I-Algorithm
.	O
</s>
<s>
The	O
motor	O
is	O
geared	O
to	O
the	O
CT	O
rotor	O
,	O
and	O
when	O
the	O
transmitter	O
's	O
rotor	O
moves	O
,	O
the	O
servo	B-Algorithm
motor	I-Algorithm
turns	O
the	O
CT	O
's	O
rotor	O
and	O
the	O
mechanical	O
load	O
to	O
match	O
the	O
new	O
position	O
.	O
</s>
<s>
CTs	O
have	O
high-impedance	O
stators	O
and	O
draw	O
much	O
less	O
current	O
than	O
ordinary	O
synchro	B-Algorithm
receivers	I-Algorithm
when	O
not	O
correctly	O
positioned	O
.	O
</s>
<s>
Synchro	B-Algorithm
transmitters	I-Algorithm
can	O
also	O
feed	O
synchro	B-Algorithm
to	O
digital	O
converters	O
,	O
which	O
provide	O
a	O
digital	O
representation	O
of	O
the	O
shaft	O
angle	O
.	O
</s>
<s>
So-called	O
brushless	O
synchros	O
use	O
rotary	O
transformers	B-Algorithm
(	O
that	O
have	O
no	O
magnetic	O
interaction	O
with	O
the	O
usual	O
rotor	O
and	O
stator	O
)	O
to	O
feed	O
power	O
to	O
the	O
rotor	O
.	O
</s>
<s>
These	O
transformers	B-Algorithm
have	O
stationary	O
primaries	O
,	O
and	O
rotating	O
secondaries	O
.	O
</s>
<s>
For	O
high	O
accuracy	O
in	O
gun	O
fire	O
control	O
and	O
aerospace	O
work	O
,	O
so	O
called	O
multi-speed	O
synchro	B-Algorithm
data	O
links	O
were	O
used	O
.	O
</s>
<s>
The	O
latter	O
was	O
called	O
a	O
36-speed	O
synchro	B-Algorithm
.	O
</s>
<s>
For	O
very	O
critical	O
applications	O
,	O
three-speed	O
synchro	B-Algorithm
systems	O
have	O
been	O
used	O
.	O
</s>
<s>
A	O
differential	O
transmitter	O
is	O
connected	O
between	O
a	O
synchro	B-Algorithm
transmitter	I-Algorithm
and	O
a	O
receiver	O
,	O
and	O
its	O
shaft	O
's	O
position	O
adds	O
to	O
(	O
or	O
subtracts	O
from	O
,	O
depending	O
upon	O
definition	O
)	O
the	O
angle	O
defined	O
by	O
the	O
transmitter	O
.	O
</s>
<s>
There	O
are	O
synchro-like	O
devices	O
called	O
transolvers	O
,	O
somewhat	O
like	O
differential	O
synchros	O
,	O
but	O
with	O
three-lead	O
rotors	O
and	O
four-lead	O
stators	O
.	O
</s>
<s>
A	O
resolver	B-Algorithm
is	O
similar	O
to	O
a	O
synchro	B-Algorithm
,	O
but	O
has	O
a	O
stator	O
with	O
four	O
leads	O
,	O
the	O
windings	O
being	O
90	O
degrees	O
apart	O
physically	O
instead	O
of	O
120	O
degrees	O
.	O
</s>
<s>
Its	O
rotor	O
might	O
be	O
synchro-like	O
,	O
or	O
have	O
two	O
sets	O
of	O
windings	O
90	O
degrees	O
apart	O
.	O
</s>
<s>
Although	O
a	O
pair	O
of	O
resolvers	B-Algorithm
could	O
theoretically	O
operate	O
like	O
a	O
pair	O
of	O
synchros	O
,	O
resolvers	B-Algorithm
are	O
used	O
for	O
computation	O
.	O
</s>
<s>
A	O
special	O
T-connected	O
transformer	B-Algorithm
arrangement	O
invented	O
by	O
Scott	O
(	O
"	O
Scott	O
T	O
"	O
)	O
interfaces	O
between	O
resolver	B-Algorithm
and	O
synchro	B-Algorithm
data	O
formats	O
;	O
it	O
was	O
invented	O
to	O
interconnect	O
two-phase	O
AC	O
power	O
with	O
three-phase	O
power	O
,	O
but	O
can	O
also	O
be	O
used	O
for	O
precision	O
applications	O
.	O
</s>
