One of two standard USB connectors, the USB Type B connector (technically known as a “Standard B” connector) is roughly square in appearance, with a squarish protrusion on top. Type B ports are found on many USB non-host devices, such as audio interfaces, external hard drives, and printers. Type B plugs are found on one end of most USB cables.
Four-pin USB Type B connections are used for USB 1.1 and USB 2.0. USB 3.0 uses a 9-pin form of Type B connection, which allows for faster data transfer. However, the pins in the USB 3.0 version are arranged in such a way that compatibility with 4-pin USB 1.1 and USB 2.0 connectors is ensured. There is also a second type of USB 3.0 Type B connection (referred to as a “Powered B connection” that has 11 pins, two of which are used to carry power. While USB 1.1 and USB 2.0 Type B connections are compatible with USB 3.0 connections, the reverse is not true — you can’t plug a USB 3.0 Type B connector into a USB 1.1 or 2.0 connection.