USB A
The number of USB inputs located on the body of the card reader or hub (see “Type”). This parameter determines the number of USB ports you will have at your disposal after connecting the device. "Pure" card readers and combined models usually have 1,
2, and even
3 USB inputs, while hubs typically feature
4 or more ports.
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.
HDMI
HDMI is the most popular of modern multimedia digital interfaces. It is specifically designed for HD content and provides the transmission of high-resolution video and multi-channel audio through a single cable.
HDMI outputs are mainly found in hubs connected via USB Type C and compatible with the Thunderbolt interface (see "Connection"). Essentially, to use HDMI, you will need to connect the device to a Thunderbolt v3 port — a "pure" USB Type C does not support video transmission. This capability may be useful if an external screen is intended for HDMI connection, but your PC or laptop lacks such ports, or they are occupied or unavailable for other reasons. HDMI can have different versions, which affects its bandwidth. For instance, to transmit 4K video at 60 fps, you need
HDMI v 2.0 or 2.1. And
multiple ports will allow you to connect more than one monitor.
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.
Cable length
The length of the cable supplied with the device. Mostly relevant for models with a non-removable cable that cannot be replaced.
