Four is a Ring World notable for its unique technological philosophy centred on mechanical automation through programmable logic controllers (PLCs). Established in 3-3102, it stands as one of the most profitable mining-focused Ring Worlds despite—or perhaps because of—its deliberate rejection of integrated circuitry in favour of electromechanical systems. The station maintains a population of approximately 1.2 million permanent residents.
The station's core systems operate through an extensive network of over 12,000 interconnected PLCs, making it the largest purely mechanical analogue computer network still in active use. These controllers manage everything from life support to industrial operations through a complex system of relays, magnetic tape storage, and precision-engineered mechanical components. The central control hub, known as the "Clockwork Heart," occupies a 3-kilometre section of the station's administrative ring and requires constant maintenance by specialised technicians.
Four's mining operations extend throughout its 38-kilometre diameter, employing a sophisticated array of PLC-controlled extraction equipment. The station processes approximately 450,000 metric tonnes of raw materials annually, with a particular focus on rare earth elements and precious metals. Despite its seemingly antiquated technology, Four consistently ranks among the top three most efficient Ring World mining operations.
The station's inhabitants are known as "Mechanists," reflecting their dedication to mechanical engineering principles. The population is strictly stratified based on technical expertise, with Master Mechanists forming the highest social class. Education on Four primarily focuses on mechanical engineering, with apprenticeships beginning as early as age 12.
The station's cultural identity is deeply intertwined with its mechanical heritage, manifesting in art forms that often incorporate moving parts and clockwork elements.