Alphabet code. “Secret” code.
A 101
B 1011
C 10110
D 101101
E 1011010
F 10110100
G 101101001
H 1011010010
I 10110100101
J 101101001011
K 1011010010110
L 1011010010110
M 1011010010110
N 10110100101101
O 101101001011011
P 1011010010110110
Q 10110100101101100
R 10110100101101100
S 101101001011011001
T 1011010010110110010
U 10110100101101100101
V 101101001011011001010
W 1011010010110110010101
X 10110100101101100101011
Y 101101100101101001010110
Z 1011011001011010010101102