Extension leads and especially the practical desk extension leads offer a useful way to connect electronic devices directly without having to look for a free socket under the desk. When choosing a extension lead with USB, however, you should pay attention to which USB port is being used. There are USB chargers and USB hubs. But what are the differences between a extenstion lead or table extension lead with charger and a table extension lead with hub?
Extension lead with USB hub
The Desktop-Power-Plus extension lead strip offers, in addition to the two Schuko sockets, a USB 2.0 hub with four type A sockets for connecting USB end devices and a type B socket for connection to the PC/notebook. This allows end devices such as keyboard/mouse, printer, USB stick and USB hard drives to be elegantly connected to the PC..
Power is supplied to the USB hub by connecting it to a PC/notebook via the type B socket.
A USB hub is a device that distributes the USB signal to multiple USB ports. USB hubs can draw their power from the bus itself (bus-powered) or have their own power supply, usually in the form of an external power supply (self-powered). Self-powered hubs have the advantage that each device connected to them can draw up to 500 mA current. With bus-powered hubs, the hub and all devices connected to it may together draw a maximum of 500 mA. The USB standard requires connected devices to start in low power mode (100 mA) and, if higher current is required, request it from the host before switching to normal mode. With USB 2.0 this can be up to a further 4x 100 mA. If this request fails, the device must switch itself off. If a host (PC) is not connected, the USB ports are not released according to USB specification. However, many USB consumers use the USB port unsolicited only as a voltage source and violate the USB standard by attempting to draw more than 100 mA current without the host's permission. This is only possible with USB hubs that do not conform to the USB specification. In this case the upstream (host) bus power supply is internally short-circuited with the external power supply not conforming to the specification. The same 5 V supply is applied to the downstream ports without protective elements. In extreme cases, this could damage the USB port of the host (PC) or disrupt the power management of the computer, which could lead to unstable behavior. Brennenstuhl products with USB hub, on the other hand, comply with the USB specifications to avoid such damage.
