USB А
The number of USB inputs located on the case of the card reader or hub (see "Type"). The number of USB ports that you will have at your disposal after connecting the device depends on this parameter. "Pure" card readers and combined models, usually, have 1,
2 and even
3 USB inputs, while hubs have
4 or more ports.
HDMI
HDMI is the most popular of today's multimedia digital interfaces. It is specifically designed for HD content and delivers high-definition video and multi-channel audio over a single cable.
HDMI outputs are found mainly in hubs connected via USB Type C and compatible with the Thunderbolt interface (see "Connection"). Actually, to use HDMI, you will need to connect the device to the Thunderbolt v3 connector — "pure" USB Type C does not provide video transmission. This feature can be useful if the external screen is designed for HDMI connection, but there are no such connectors in the PC or laptop itself, they are busy or unavailable for another reason. At the same time, HDMI can be a different version, which affects the throughput. So to transfer video in 4K at 60 fps, you must have
HDMI v 2.0 or 2.1.
External power supply
External USB devices require power to work, which is supplied to them through the same USB port. However, the power of such power supply is relatively low (especially in version 2.0 ports, see "Connection"), and if several external devices are connected to one port of the computer through a hub, a situation may arise when the power is not enough for their operation.
Connecting an external power supply to the hub allows you to avoid such situations: the hub receives additional power from the network and supplies power of the appropriate power to each of its inputs.
Another option for using devices with this function is charging portable equipment via USB: some models can work as stand-alone chargers that do not require connection to a computer.
Power Delivery
The technology allows you to work at higher voltage, thereby increasing the transmitted power.
USB hubs with Power Dlivery can not only charge smartphones faster, but also power more power-hungry devices, such as laptops.
Cable length
The length of the cable supplied with the device. Mostly relevant for models with a non-removable cable that cannot be replaced.
