The document is a service manual that provides information on maintenance and repair of hydraulic excavators models ER 900-942. It contains sections covering general information, tools, technical data, maintenance guidelines, the engine, coupling and splitterbox, hydraulic system, hydraulic components, electrical system, swing gear, swing ring, travel gear, track components, axles, cab heater/air conditioning system, undercarriage and uppercarriage attachments, and special attachments. The manual is intended to aid owners and technicians in servicing and repairing the excavator models.