linguistic:paraphrasing, information:classification
Three-bank typewriters

Certain models further reduced the number of keys and typebars by making each key perform three functions – each typebar could type three different characters. These little three-row machines were portable and could be used by journalists.

Such three-row machines were popular with WWI journalists because they were lighter and more compact than four-bank typewriters, while they could type just as fast and use just as many symbols.

Such three-row machines, such as the Bar-Let and the Corona No. 3 Typewriter have two separate shift keys, a "CAP" shift (for uppercase) and a "FIG" shift (for numbers and symbols).

The Murray code was developed for a teletypewriter with a similar three-row typewriter keyboard.