This TENs comes with power plug adapter & battery..
http://www.amazon.com/PM-745-Electro...+power+adapter


I really like my IF stim, I use it on my neck/trap/shoulder muscles and low back/hip too.

Interferential (IF) is like TENS , but less zap/stinging..

https://www.google.com/search?q=Inte...ial&gws_rd=ssl

Info on the differences between TENS, IF and others types-
http://vitalityweb.com/backstore/Muscle-Stimulator.htm