Abstract: This invention provides a printer, having an elongate platen and a print head carriage adapted for relative movement therebetween longitudinally of the platen, in which a position indicator ascertains the position and direction of motion of said carriage longitudinally of said platen. The indicator comprises an optical position encoder rotatably mounted on an axis fixed longitudinally of said platen, and a carriage position responsive means connected to said carriage and said encoder to transmit said relative movement to said encoder to rotate said encoder in synchronism with said relative movement. The encoder has a pattern of detectable indicia and a detector is responsive to said indicia to provide a signal indicative of said position.