Devices in this family are used in conjunction with microcontrollers, microprocessors, or similar devices for the purpose of increasing the number of signal connections available for connecting peripheral devices. The typical concept of operation involves the use of serial communications requiring only a few I/O lines on the host device to read/write the status of many input/output pins on the expander device. The technique exchanges speed of communication for increased connectivity, and is best suited for applications where fast response is not critical, such as in many human interface applications.