The iButton is an electronic chip armoured in a 16mm stainless steel can. Because of this unique, durable package, up-to-date information can travel with a person or object. The stainless steel button is rugged enough to withstand harsh outdoor environments; it is durable enough for a person to wear everyday
on an accessory like a ring, key fob, wallet, watch, metal card or badge. It is also waterproof and so can be worn while washing or swimming.
The information within the iButton can be read by ‘tapping’ it against a simple ‘two-contact’ metal probe connected to the electronic reader circuit. This type of metal probe is much more durable than a magnetic swipe or ‘smart-card’, and the iButton has a much larger memory capacity. Every iButton produced has a unique serial number - to date over 50 million iButtons have been manufactured. This serial number means that every single iButton can be uniquely identified -no two iButtons will ever have the same number. This feature makes the iButton ideal for use as a ‘key’ or ‘tracking device’ - there will never be another key with the same serial number, and it would be very hard for an impostor to ‘fake’ a duplicate key. The serial number is 14 digits long and, so that it can also be read by humans, it is also laser engraved on the bottom of the stainless steel can.
How does the iButton work?
The silicon chip inside the stainless steel can is connected via two internal wires to the sides and front face of the iButton. When the iButton is momentarily touched against a probe, the side makes a ground (0V) connection, and the face makes a power/data connection. In a fraction of second the iButton ‘steals’ enough power from the probe to operate, and then transmits information (such as the serial number) via the same single connection. Because power and data are transmitted via the same wire, this type of connection is commonly referred to as a ‘1-wire’ interface. This ‘1-wire’ interface means that most iButtons do not need an internal battery - they simply get the power they require to operate by touching against the reader probe. This means the devices never ‘run-down’, and because of the robust stainless steel can, they are extremely durable. The iButton can transmit a large amount of information in a very short time - for instance it is almost impossible to ‘tap’ an iButton against a probe quicker than the time required by the iButton to transmit it’s serial number! This makes the iButton an ideal device for applications such as locks where data has to be transmitted very quickly.