Video switchers accept multiple video inputs and control display-sequence switching from video sources such as cameras and video servers. Sequencing is often user-defined and varies in terms of dwell time, display order, and sequencing mode. Video switchers consist of a main control panel that serves as the user interface and a rack unit (RU) of printed circuit boards (PCB) that perform various functions based on user input. Standard devices are connected in parallel to existing control switches or use serial communication interfaces such as RS232 or RS422. Wireless products use infrared (IR) transceiver systems. Most video switchers support standard definition (SD) video, high definition (HD) video, or both SD and HD. Devices use 115 VAC or 230 VAC and provide programmable logic, digital signal processing (DP), four or more duplex-transceiver channels, and high-speed data transmission rates.