IPhone 3GS and quad-band GSM/GPRS/EDGE radio, the 3GS also adds support for 7.2 Mbit/s HSDPA allowing faster downlink speeds though upload speeds remain the same as Apple had not implemented the HSUPA protocol. Other updates include the addition of a built-in Nike+iPod sensor which eliminates the need for an external sensor and allows native Nike+iPod support. The Bluetooth server on the iPhone 3GS has also been slightly improved adding support for Bluetooth 2.1 specifications. Voice Control was introduced as an exclusive feature of the iPhone 3GS and allows for the controlling of the phone and music features of the phone by voice.
IPhone placement of the microphone and speaker on the base on the unit—the speaker is on the right. Volume controls are located on the left side of all iPhone models and as a slider in the iPod application. The 3.5mm TRRS connector for the headphones is located on the top left corner of the device for the first five generations (original through 4S), after which time it was moved to the bottom left corner. The headphone socket on the first-generation iPhone is recessed into the casing, making it incompatible with most headsets without the use of an adapter. Subsequent generations eliminated