Laptop dock connector
Docking connectors for laptop computers are usually embedded into a mechanical device that supports and aligns the laptop and sports various single function ports and a power source that are aggregated into the docking connector. Early docking connectors would carry keyboard, serial, parallel, and video ports from the laptop and supply power to it. Often these ports were available on the laptop itself, giving rise to the term "port replicator" for simpler docks. More complicated docks are usually termed docking stations, but both will have some sort of docking connector. As laptop interfaces evolved, so did the functions carried by the dock connector. The keyboard and serial ports changed to PS/2 connector for the keyboard and mouse. Now, USB is almost universal and DVI is common. eSATA and FireWire ports are also carried through the docking connector.
Portable media player dock connector
An Apple Dock Connector
Many Portable media players feature a dock connector, such as the Apple dock connector, which is a proprietary 30-pin connector that is common on most models of iPods, and all models of the iPhone and iPad.Originally, the Apple dock connector carried USB, FireWire, some controls and line-level audio outputs. As the iPod evolved, so did the signals in the dock connector. Video was added to the connector. FireWire was phased out of the iPods, which led to a discontinuity in usage of the dock connector. Older implementations of the dock connector may have been using the FireWire power pin to supply power, and cannot charge later iPods, iPhones, or the iPad, requiring an after market adapter to allow charging.
The simplest form of the dock connector today takes the form of a simple cable with the dock connector on one end and a USB connector on the other. This cable only has the USB signals in the dock connector, but is sufficient to synchronize and charge the devices. At the other end of the spectrum, dock connectors are used to completely merge devices into a variety of accessories, both mechanically and electrically.
Because of the popularity of portable media players, many third parties have used dock connector interfaces for accessories. This includes many variations of external speakers, including stereo systems and clock radios. Automotive accessories for the portable media players are numerous and include charging cradles, FM transmitters for playing audio through the car's speakers and a full GPS receiver. There are also original and aftermarket cables with dock connectors for direct integration with the car's audio system and controls.