Visible Speech is a writing system invented in 1867 by Alexander Melville Bell, father of Alexander Graham Bell, the inventor of the telephone. Melville Bell was a teacher of the deaf and intended his writing system to help deaf students learn spoken language.
Visible Speech was also the first notation system for the sounds of speech independent of a particular language or dialect and was widely used to teaching students how to speak with a "standard" accent.
Visible Speech symbols are intended to provide visual representations of the positions the organs of speech need to be in to articulate individual sounds. Once the underlying principles are understood it is apparently fairly straightforward.