A Device Type Manager (DTM) is part of the FDT standard that is a software component for a device that contains the device-specific data, functions and logic elements. DTMs can reach from a simple graphical user interface for setting device parameters up to a highly sophisticated application that, for example, can perform complex calculations for diagnostics and maintenance purposes or can implement arbitrarily complex business logics for device calibration.

The DTM also contains FDT-compliant interfaces to enable communication with the connected system or tool.  DTMs are classified as Device DTMs, which represent a field device, and CommDTMs, which represent communication components (gateways, remote I/Os, couplers, etc.).
A typical FDT based application will contain dozens, hundreds, or thousands of Device DTMs and CommDTMS from a variety of manufacturers to make up the system.