Abstract: A serial printing device comprises a type head mounted rotatably on a carriage which is slidable along a printing line of an office machine. A continuously rotating driving shaft is connected to a differential mechanism which normally transfers the motion to the type head for the selection of the character to be printed. A selectively actuatable electromagnet arrests the rotation of the head in the printing position and simultaneously transfers the motion of the driving shaft to a striking mechanism to effect the printing of the selected character. A positioning element, commanded by the striking mechanism at the actuation of the electromagnet, keeps the head locked during the striking movement and the electromagnet is immediately deenergized. After the striking of the selected character the head is freed by the positioning element and is set in rotation again.