The document is a service manual that provides technical data, maintenance guidelines, and information on systems for hydraulic excavators models ER 900-942. It covers general information, tools, the engine, coupling and splitterbox, hydraulic system, hydraulic components, electrical system, swing gear, swing ring, travel gear, track components, undercarriage and uppercarriage attachments, cab heater and air conditioning. The manual is intended to assist with maintenance and repairs for the excavator models.