The iButton serial number (DS1990A) is a rugged data carrier that serves as an electronic registration number for automatic identification. Data is transferred serially through the 1-Wire protocol, which requires only a single data lead and a ground return. Every DS1990A is factory lasered with a guaranteed unique 64-bit registration number that allows for absolute traceability. The durable stainless-steel iButton package is highly resistant to environmental hazards such as dirt, moisture, and shock. Its compact coin-shaped profile is self-aligning with mating receptacles, allowing the DS1990A to be used easily by human operators. Accessories enable the DS1990A to be mounted on almost any object, including containers, pallets, and bags.