RFID tags and readers/encoders employ specific air-interface protocols (essentially, the language the two use to communicate). There are a variety of international standards for air-interface protocols. Some are for high-frequency (HF) tags and readers/encoders, some cover ultrahigh-frequency (UHF) and some are for active RFID systems.
If you have tags and interrogators that operate at the same frequency and utilize the same air-interface protocol, they will be able to communicate, regardless of the manufacturer. However, you cannot pick up a UHF reader and expect to read HF tags, or use an ISO 15693 HF reader to interrogate ISO 14443 HF tags.
Fixed UHF readers/encoders can be purchased for $800 and up, while handheld UHF models are more expensive. HF interrogators are usually a little cheaper. I am unaware of any place where you can purchase refurbished units—but perhaps our readers might know of one and can post that information below.
—Mark Roberti, Editor, RFID Journal