IPhone 4 models. In fall 2010, pentalobe screws started to replace the Philips screws used in post-repair units in the US and in production units in Japan. The iPhone 4 shipped with iOS 4, which was the newest version of Apple's iOS mobile operating system at the time. iOS 4 introduced a multitasking system, allowing apps to remain "suspended" in memory, perform certain operations in the background, and allowing users to switch between apps using an on-screen menu. It also introduced FaceTime, which allows users to perform video calls between other iPhone, iPad, iPod Touch, and OS X users. The iPhone 4
IPhone accessories for phone calls and voice control of certain devices. Users can adjust volume, control music and video playback (play/pause and next/previous,) and record voice memos on supported iPod and iPhone models and Mac computers. There have been many reports of moisture problems with the remote/mic earbuds. The original iPhone and iPhone 3G came with the iPhone Stereo Headset, a push-button and microphone on the right side of the headphones (there is no volume control, and only limited control of calls). A series of docks released for the iPhone 5, 5s, and 5c, were announced and released on September 10, 2013.