The iButton / Dallas key is perfect for EPOS systems in retail and catering. Great for use in bars, restaurants, and retail stores. The iButton contains a 1990A-F5 Integrated Circuit chip, sealed in the stainless-steel cover. It is waterproof, shockproof and corrosion proof. Data is transferred serially through the 1-Wire protocol, which requires only a single data lead and a ground return. The durable stainless-steel i-Button package is highly resistant to environmental hazards such as dirt, moisture, and shock. Working temperatures: -40 degrees to 90 degrees.