06 What is the International Alphabet No. 5?

ITA-5 is a 7-bit code in addition to ITA-2.

T.50 : International Alphabet No. 5 (itu.int)

This recommendation specifies a set of 128 characters (control characters and graphic characters like
letters, numerals and symbols) with their coded representation.

Most of these characters are
mandatory and unchangeable.

However, some flexibility is provided to meet national and other requirements.