Headscratchers / Star Trek S1 E11 "The Menagerie, Part I"

• Pike cannot speak normally and can only flash a yes/no light. Why couldn't they use a simple alphabet (by numbers), Morse code, or even easier, a prisoner's square, to have him convey words to tell them of the emergency.
  • 1960s technology? In-universe though? It could be related to the effects of the radiation that caused his condition.