A bus exchange switch is a device that switches a digital bus. They can provide for the multiplexing of data buses, memory interleaving and switching or buffering buses on system backplanes. They are available in a full range of bit widths from one bit up to 32bits wide. They typically support very low propagation delays.

Bus exchange switches are arrays of FET switches that can perform various functions including the physical isolation of two buses, the translation of voltage levels, differing interface standards between buses and the switching exchange of data between buses, known as a crossbar. They can also operate as buffers, extending the length of a bus by isolating and re-driving the capacitive loads of part of a bus.

Important characteristics of a bus exchange switch include an impedance of the input and output ports and the resistance of the series circuit. These buses can also be differential rather than single-ended interfaces. When the bus comprises of transmission lines, the bus exchange switch needs to provide a good impedance match in order to prevent unwanted signal reflections on the bus that may lead to data corruption.  With non-transmission line circuits, the series resistance is an important characteristic because it forms a voltage divider that will attenuate the signal. In this case, the on resistance (ron) needs to be as low as possible. Another important characteristic is the time it takes to switch the bus connections to the desired state.

Bus exchange switches may offer additional features like the ability to hold a bus level that was present on its input before the inputs went to a high impedance state. This prevents the situation where the buses floats at undetermined levels that will generate noise, metastable states and cause increased consumption of power. They can also have integrated series resistors that facilitate matching with transmission lines to reduce signal reflections. Many bus exchange switches can survive powered on connection or disconnect a bus called hot-swapping.