Merchant Service Harware vs POS Hardware

[joefut2]

Ive been researching POS systems and Merchant services for several weeks now, as you can tell by my posts on this site. Ill start this off by stating im currently overseas, so a phone is not an option for me. Most of the times I contact a POS or MS company, they reply with a number to call back and never answer my question via email. The reoccurring question I have, which is very novice and prob equally as dumb to you guys is POS hardware bundles usually come with a card swiper, and most MS companies also sell you a card swiper for processing credit cards etc. YOu can only use one correct? Is it necessary to purchase the MS cardswiper if yo have one for the POS already? I have read they can be reprogrammed, but the details have been vague at best.

Thank you all for your help

Joe