The document is a product selection guide from ServoTek Products that includes information about their tachometers, encoders, and transducers. It describes ServoTek as a manufacturer of instrument-grade DC tachometers and encoders for aerospace, automotive, industrial, and other applications. It provides specifications for their various tachometer models, which are grouped by series based on armature length and output voltage. Mounting dimensions and technical specifications are also included to help customers select the appropriate product for their needs.