An electrocautery device passes an electric current through an electrode, causing it to become hot. This can be used for branding to create patterns more intricate than is possible using the traditional strike branding method. Patterns chosen cannot be extremely detailed as there is a certain amount of heat damage done to surrounding tissues. Expect the lines in any brand done to spread while healing to around three times their initial width.
A variety of electrodes are available, making different widths of line easy to accomplish.
A cautery pen is a small battery powered electrocautery unit, but tends not to be powerful enough for anything more than the smallest branding project.
For branding designs of too great an intricacy for electrocautery branding, electrosurgical branding (sometimes called hyfrecator or laser branding) is a superior alternative.