Oldtech refers to technologies which are obsolete or significantly behind the technological standards of the 'Verse. They are usually found in the hands of frontier colonists on the Rim planets or among the poorest elements of Border world society.
While more advanced technologies exist, and a wide range of tech levels are known in the 'Verse, the use of oldtech persists because such devices are generally cheap, easy to produce with primitive tools and limited resources, and do not require super-skilled craftsmen to build and maintain.