Knowledge base

USB Cable Maximum Length - Data considerations

USB-IF standard recommended below length for USB cables for data transfer

*reference from USB standard

The USB standard was originally intended to connect desktop computers to peripherals such as printers, mice, keyboards and storage devices. The distance between devices was typically short. Fast forward to the present and USB cables have found applications well beyond the desktop. For example, it’s not uncommon for the USB‑C port on a laptop to be connected to a wall-mounted display 30-feet away, or a camera in a hallway to be connected to a computer inside an office. You can now lengthen USB connections with select cables and extenders. Let’s take a closer look at USB cable length limits, the technology, and how to extend a USB connection without losing signal strength. Why do USB Cables Have a Maximum Length? Most communication protocols used to transfer data between computers and other devices use a signaling method called duplex, including Ethernet and USB. Devices connected in a duplex system can communicate with each other in both directions. So when a USB host sends a “packet” of data to a device connected by a USB cable, it waits for a response before sending the next packet. If no response is received, it tries sending the packet again. Clearly, timing is very important. As the data transfer rate goes up, the USB host has less time to transmit its data packets and receive a response. The further the signal has to travel, the more likely that an error called a “late collision” will occur, so high data transfer rates typically require a shorter cable. USB

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