Why not directly use the area code or national standard code as the internal code?
The range of area and location numbers is 1~94. After adding 32, the code value is between 33~ 126. This avoids the control character spacing of ASCII code. If the system doesn't take advantage of men's processing power and treats the right 7 bits of men's inner code bytes as characters, it's just an error in printing characters, and the confusion may not be so serious.