It sounds like you have a Samsung ER-5100 with a general input error. Turn to each mode and press clear to see if it stops in any mode. If it does, then that mode is the one you were last working in and you need to finish before turning the key. E.g Turn to REg mode, press CLEAR. Turn to X mode, press CLEAR until it stops beeping. If it won't stop, it may have been left off for too long or have a bad battery and need a full re-program.
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If anyone needs / looking for a samsung or Sam4s ER-5100 manual, go here:
http://the-checkout-tech.com/manuals/cashregisters/samsung1.php
Registerman, July 2010
