Chorded keyboard (a writing system for the blind) uses either 6 or 8 tactile 'points' from which all letters and numbers are formed. When Louis Braille invented it, it was produced with a needle holing successively all needed points in a cardboard sheet. In 1892, Frank Haven Hall, superintendent of the Illinois Institute for the Education of the Blind, created the Hall Braille Writer, which was like a typewriter with 6 keys, one for each dot in a braille cell. The Perkins Brailler, first manufactured in 1951, uses a 6-key chord keyboard (plus a spacebar) to produce braille output, and has been
Blind Approach Beacon System to fly left or right and indeed up or down with a co-located glidepath (328.6 to 335.4 MHz) equipment. See instrument landing system for further details. Blind Approach Beacon System A blind approach beacon system or beam approach beacon system (BABS) is an automatic radar landing system developed in the early 1940s. It is a responder (or transponder) mounted in a Hillman van and placed at the end of the runway. In some cases fixed sites were installed and by the mid-1950s Standard 9 vans were in use. It was interrogated by a "Rebecca" unit mounted in an aircraft. It