Hardware
Screen and input
The iPad's touchscreen display is a 9.7 in (25 cm) liquid crystal display (1024 × 768 pixels) with fingerprint-resistant and scratch-resistant glass. Like the iPhone, the iPad is designed to be controlled by bare fingers; normal gloves and styli that prevent electrical conductivity may not be used,[25] although there are special gloves and capacitive styli designed for this use.[26][27]
The display responds to two other sensors: an ambient light sensor to adjust screen brightness and a 3-axis accelerometer to sense iPad orientation and switch between portrait and landscape modes. Unlike the iPhone and iPod touch built-in applications, which work in three orientations (portrait, landscape-left and landscape-right), the iPad built-in applications support screen rotation in all four orientations (the three aforementioned ones along with upside-down),[28] meaning that the device has no intrinsic "native" orientation; only the relative position of the home button changes.
In total there are four physical switches on the iPad, including a home button below the display that returns the user to the main menu, and three plastic physical switches on the sides: wake/sleep and volume up/down, plus a third which, as of iOS 4.2, acts as a mute switch.[9] Initially this switch was utilized to lock out the screen rotation function (reportedly to prevent unintended rotation when the user is lying down).[29] However, with the iOS 4.2 update, this functionality was removed and rotation lock is now controlled with a software toggle via the iOS task switcher. There is no means to reassign the physical switches functionality in the official iOS release.
Connectivity
The iPad can use Wi-Fi network trilateration from Skyhook Wireless to provide location information to applications such as Google Maps. The 3G model contains A-GPS to allow its position to be calculated with GPS or relative to nearby cellphone towers; it also has a black plastic accent on the back side to improve 3G radio sensitivity.[31]
For wired connectivity, the iPad has a proprietary Apple dock connector; it lacks the Ethernet and USB ports of larger computers.[9]
The iPad has two internal speakers that push mono sound through two small sealed channels to the three audio ports carved into the bottom-right of the unit.[12] A volume switch is on the right side of the unit.
A 3.5-mm TRS connector audio-out jack on the top-left corner of the device provides stereo sound for headphones with or without microphones and/or volume controls. The iPad also contains a microphone that can be used for voice recording.
The built-in Bluetooth 2.1 + EDR interface allows wireless headphones and keyboards to be used with the iPad.[32] However, the iOS does not currently support file transfer via Bluetooth.[33] iPad also features 1024 x 768 VGA video output for connecting an external display or television.[34]
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