To clear Sharp printer errors, turn off at the power. Make sure key is in REG mode. Turn on at power. Press CLEAR (CL). If error returns immediately, there is still a printer fault or jam.
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If anyone needs a Sharp UP-700 manual, one of our users has Operation, programming and service manuals here:
http://the-checkout-tech.com/manuals/cashregisters/Sharp10.php
Registerman, February 2013