Equipments connected at the end of dedicated lines, more especially modems and associated calculators, can be destroyed when excess-voltage occurs on the communication line. This excess-voltage, coming for example from stormy weather, induces interactions between the power supply and the telephone line, jeopardizing hardware and placing the user's health at risk. Up until now, the only solution was to bypass the excess-voltage, using grounded lightning arrestors, which proved to be expensive to install and maintain.
Terminal equipment operates as if it was no longer connected to the power supply.
The protection comes from the high dielectric rigidity barrier installed in the device.