INTRODUCTION In order to ease the equipment design engineer's problem and at the same time provide a basis for comparing measurements by manufacturer and user this recommended practice sets up standard test procedures for acceptance testing. These conditions and the basic tests to which the characteristics refer are grouped in Section 2 and compose a complete list of defining characteristics of the synchro. Specifications written around synchros have specified certain necessary characteristics for production acceptance testing@ such as null voltage and accuracy@ under test conditions and techniques that are mainly and properly concerned with accuracy and the shortest possible test time. These characteristics are inherently temperature sensitive and therefore these characteristics are degraded when the synchro is operating for a period of time at other then room temperature. In synchros this degradation is a factor of high importance. The amount of change for a given temperature variation@ will vary with frame size and internal design@ so that it is not practical to assign a definite limiting percentage value of degradation of either synchros as a class@ or to frame sizes. Since environmental testing as a whole is impractical for 100% production testing or incoming inspection testing@ an additional section 2.4 (Environmental conditions) has been provided.