Connection to live device with VCC connection

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HMIs, human machine interfacesET-208Electrical Installation ET-208Connection ofExternal USB devicesConnection in hazardous areaConnection to live device with VCC connection


An external USB device can be connected at terminal X4.


The USB device has to meet the requirements for connection to an Ex(e)  interface and must be mounted inside an explosion-protected enclosure.


The USB device does require an external power supply to function because it uses over 500 mA.

The USB device is connected to the mains via other interfaces.

The USB device needs the VCC connection of the HMIs (internal supply – terminal 1) to function.


HMI USB Ex(e) connector


cable glands

e. g. Ex d housing

USB - device *2


power supply


equipotential bonding for shield connection

USB cable twisted data wires


USB(e) device

Connected to mains via power supply

or other interfaces.



Data cable wires must be twisted right up to terminal.


e.g. USB/serial converter, USB-Profibus interface.



See also:

Kapitelseite X4 - USB(e)

Kapitelseite External USB devices



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