On the Subject of Not Knobs

Even more complicated and extremely needy. Imagine if such expertise were used to make something other than tampered modules.

The knob can be turned to one of four different positions.
Each position will show a different pattern on the twelve LEDs.
The six LEDs on the left show a Braille letter rotated anticlockwise, while the six LEDs on the right show a Braille letter rotated clockwise.
Exactly one position will be valid according to its rule below. The knob must be in this position when the timer hits zero.

Knob positions are relative to the ‘U’ label, which may be rotated.

• The up position is valid if both letters are in the bomb’s serial number.
• The right position is valid if only the right letter is in the bomb’s serial number.
• The down position is valid if neither letter is in the bomb’s serial number.
• The left position is valid if only the left letter is in the bomb’s serial number.

Braille Letters

Lit LEDs represent filled dots in the table below.

a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

p

q

r

s

t

u

v

w

x

y

z