Keeping in contact

Some computers use infrared beams to exchange data with other computers. But
the light path can easily be blocked. NEC of Japan suggests a simple solution
(GB 2 312 800). The infrared source and receiver are built into a capsule at the
end of a wire, which is wound on a spring-loaded spool. It can be extended and
retracted as needed, so that the infrared beam is never broken.