<s>
In	O
electrical	O
control	O
engineering	O
,	O
a	O
stepping	O
switch	O
or	O
stepping	O
relay	O
,	O
also	O
known	O
as	O
a	O
uniselector	B-Algorithm
,	O
is	O
an	O
electromechanical	O
device	O
that	O
switches	O
an	O
input	O
signal	O
path	O
to	O
one	O
of	O
several	O
possible	O
output	O
paths	O
,	O
directed	O
by	O
a	O
train	O
of	O
electrical	O
pulses	O
.	O
</s>
<s>
Code	O
breakers	O
at	O
Bletchley	O
Park	O
employed	O
uniselectors	B-Algorithm
driven	O
by	O
a	O
continuously	O
rotating	O
motor	O
rather	O
than	O
a	O
series	O
of	O
pulses	O
in	O
the	O
Colossus	O
to	O
cryptanalyse	O
the	O
German	O
Lorenz	O
ciphers	O
.	O
</s>
<s>
In	O
a	O
uniselector	B-Algorithm
,	O
the	O
stepping	O
switch	O
steps	O
only	O
along	O
or	O
around	O
one	O
axis	O
,	O
although	O
several	O
sets	O
of	O
contacts	O
are	O
often	O
operated	O
simultaneously	O
.	O
</s>
<s>
In	O
other	O
types	O
,	O
such	O
as	O
the	O
Strowger	B-Device
switch	I-Device
,	O
invented	O
by	O
Almon	O
Brown	O
Strowger	O
in	O
1888	O
,	O
mechanical	O
switching	O
occurs	O
in	O
two	O
directions	O
,	O
across	O
a	O
grid	O
of	O
contacts	O
.	O
</s>
<s>
An	O
electromagnet	O
advances	O
(	O
steps	O
)	O
the	O
wipers	O
to	O
the	O
next	O
position	O
when	O
fed	O
with	O
a	O
pulse	B-Algorithm
of	O
DC	O
.	O
</s>
<s>
Some	O
uniselector	B-Algorithm
designs	O
step	O
on	O
application	O
of	O
the	O
operate	O
pulse	B-Algorithm
;	O
others	O
step	O
on	O
its	O
removal	O
.	O
</s>
<s>
Single-axis	O
stepping	O
switches	O
are	O
sometimes	O
known	O
as	O
uniselectors	B-Algorithm
.	O
</s>
<s>
Slightly	O
more	O
complicated	O
was	O
the	O
two	O
axis	O
stepping	O
switch	O
,	O
(	O
also	O
called	O
Strowger	B-Device
switch	I-Device
or	O
two	O
motion	O
selector	O
in	O
Britain	O
)	O
.	O
</s>
<s>
Or	O
by	O
feeding	O
the	O
stepping	O
contact	O
with	O
an	O
endless	O
pulse	B-Algorithm
train	O
via	O
a	O
relay	O
,	O
and	O
controlling	O
the	O
relay	O
from	O
the	O
switch	O
's	O
own	O
output	O
,	O
it	O
can	O
be	O
made	O
to	O
automatically	O
hunt	O
for	O
the	O
first	O
unpowered	O
line	O
(	O
or	O
powered	O
,	O
depending	O
on	O
whether	O
the	O
relay	O
is	O
normally	O
open	O
or	O
normally	O
closed	O
)	O
.	O
</s>
<s>
They	O
could	O
also	O
be	O
used	O
as	O
a	O
demultiplexer	B-Protocol
,	O
so	O
that	O
two	O
input	O
lines	O
could	O
control	O
a	O
number	O
of	O
output	O
devices	O
.	O
</s>
