voltage is provided after a ~40 kOhm load is applied for one second. The outer large pins are ground. The tiny center pin is a data pin using the 1-Wire protocol. The computer uses this pin to change the LED's color and retrieve the serial number and wattage of the power supply. Only two wires, power and ground, go to the charger unit. There is no data communication via the adapter sense pin with the charger unit itself. The maximum voltage supplied is as follows: 14.5 V DC for the 45 W units supplied with MacBook Air 16.5 V DC for the 60 W units supplied with MacBook and 13" MacBook Pro 18.5 V DC for the 85 W units supplied with 15" and 17" MacBook Pro 20 V DC for the 85 W units supplied with 15" MacBook Pro Retina The rectangular metal shroud surrounding the pins acts as shielding for the electrical pins and a ferrous attractor for the magnet in the laptop. Third-party products Apple does not license the MagSafe connector to third-parties, though manufacturers devised a workaround: their MagSafe items use the actual connector from Apple's AC adapter, grafted onto their own products. Since this uses an actual Apple product, purchased legally, manufacturers believe that no licensing agreements are needed (a principle referred to as the first sale doctrine) and no patent was violated. However, in 2010 Apple still sued one such manufacturer, Sanho Corporation for selling its very popular HyperMac battery extension products which Apple claimed violated their patents. Sanho has since ceased to sell their connector cable for the HyperMac series of external batteries. Some fake MagSafe 2 chargers have appeared on sites such as Amazon. These chargers are often unsafe, have spelling mistakes on the charger itself, and/or have inconsistencies that the official product does not contain, e.g. the LEDs on the connector do not follow the correct color code, or the charger is referred to as a MagSafe 1 charger rather than the second generation charger. Defects Many users have reported () problems with the quality of the construction of the MagSafe cords, giving the product low marks on the Apple Store's website. Common complaints included plug separating from the cord, transformer shorting, and pin springs losing elasticity. Several methods have been devised to protect the MagSafe from failure, including wrapping the cable with tape or sliding protective plastic around the cable.