The Electrical Patents Index (EPI) Manual Codes User Guide, assists with use of the classification and indexing scheme, which Derwent applies to electrical and electronic patents. These codes, assigned since 1981, form a hierarchical indexing system, and are used to search DWPI on various platforms, such as the online hosts and Derwent Innovation.

The coding manual also includes Mechanical Transportation Q codes applied from DWPI update 200601 to highlight mechanical application or patents with mechanical novelty. From DWPI update 201201 Q Manual Codes have been further enhanced to include section Q3 – Conveying, Packaging and Storing. The Q codes are designed to be used in conjunction with one another, and also in combination with the electrical manual codes when appropriate.

GMPI & EPI Manual Codes 2024