From V&A Collections website: 
The Azimuth Co-ordinator was a joystick device for controlling a quadraphonic sound system. By swivelling the joystick, the sound output could be shifted from one speaker bank to another; with the joystick in the central position, the sound output would be equal in all speakers. It was used almost exclusively by Pink Floyd, in conjunction with a quadraphonic sound system, and was operated by keyboardist Rick Wright.
This equipment was used at the band's 1969 Royal Festival Hall concert and was one of Pink Floyd's first uses of quadraphonic sound in a live environment. The surround sound technique utilised a four speaker system, with a speaker positioned in each corner of a room. In a live performance four banks of speakers were used. Pink Floyd would later go on to develop and champion the quadraphonic system for their album Dark Side of the Moon.
Quadraphonic sound never took off to any large extent, however, despite its availability to the home consumer. In 2003 Dark Side of the Moon was re-released, this time in 5.1 surround sound, the updated and more successful progression from quadraphonic sound. Consumer technology had, by this point, caught up with Pink Floyd's early sound experimentation.

See Quadrophonic page for more