A ribbon supply apparatus including a support in which a ribbon supply spool and a take-up spool are rotatably mounted. The supply and take-up spools and the support are designed so that these spools can be mounted in the support in only one way, the correct way. The ribbon is supplied on a tubular core...http://www.google.com.tw/patents/US5433539?utm_source=gb-gplus-share專利 US5433539 - Control of media movement using a periodic calibration method and apparatus
