When torque motors are used in machine tools, it is often necessary to classify the encoders for safety-related applications according to SIL 2 (according to EN 61508) or PL d (according to EN ISO 13849), as the rotary axes are usually operated with just one encoder. The functional safety versions of the ECA 4000 modular angle encoders with bidirectional EnDat 2.2 interface from Heidenhain can be used as single-encoder systems in conjunction with a safe controller. In addition to the data interface, the mechanical coupling of the encoders is also relevant to safety. In the functional safety version of the angle encoder, the mechanical fault exclusion for safety-related applications has been confirmed as part of a type examination for a wide range of applications and is therefore guaranteed under all specified operating conditions. For example, the material and surface properties of shafts and flange components, screw lengths, screw locking devices and tightening torques are defined. The angle measuring device is available with a variety of diameters and in two drum shapes. The drum shape 'ECA 4400' is centered and attached to the customer's shaft via a press fit. If no mechanical fault exclusion is required for the safety concept, the press fit can be dispensed with. In this case, the reel form 'ECA 4402' with three-point centering can be used. Using the external interface box 'EIB 2391S', the devices can also be used in safety-related applications with a 'Drive-Cliq' interface.