An LED/photodetector structure is disclosed positioned to cooperate with a daisy wheel print element of a daisy wheel printer and a light interrupter such that under microprocessor control, a stepping motor will rotate and home the daisy wheel print element, sense the escapement pitch corresponding to...http://www.google.co.uk/patents/US4541746?utm_source=gb-gplus-sharePatent US4541746 - Initializing apparatus for daisy wheel printer
