This is a 12V fixed-voltage MyVolts-branded power supply designed to meet exactly the power specification of your Qnap TS-231P, TS-228 NAS. Specifications: - Output voltage is 12V - Max. output amperage is correct for your device - Output tip is the right size and specification - we've tested it thoroughly - 2 pin plug for use with US (Type A) wall sockets - Input voltage is 100-120V AC, 50/60Hz In addition, this -branded replacement power supply for Qnap TS-231P, TS-228 NAS is: - Compliant with all safety standards, and features overvoltage, overcurrent and short-circuit protection to protect your device from damage - Energy Star level 6 approved, guaranteeing more efficient delivery of power to your devices, at less cost to you - RoHS and CE-certified - Covered by a 2 years' warranty: if the power adaptor fails within 2 years from purchase, we'll replace it, no worries.