Abstract: The present invention discloses a dot printer in which means are provided for detecting deterioration of dot print elements which print characters and so on and for detecting trouble caused by a print drive circuit. Print sensing elements are placed at a suitable point of a platen corresponding to a traverse range of dot print elements which are housed within a printing head and a mechanism for driving each dot print element is provided when said dot print elements move in front of the above-said print sensing elements sensing signal is generated when said dot print elements effect printing on the print sensing elements, to indicate the existence of trouble of the print drive circuit or dot print elements.

Abstract: This invention provides an ink mist type high speed printer comprising a first electrode and a second electrode between which a high voltage is applied, and an aperture board disposed between the first and second electrodes and adapted to selectively control passage of the ions generated from the second electrode, wherein a stream of ink mist is passed between the aperture board and first electrode so that the ions which have passed the aperture board will selectively charge the ink mist particles to let the charged ink mist particles deposit on a recording paper placed between the ink mist and first electrode to thereby print a desired dot matrix character.