In a telecommunications system, a switching device selectively applies one of two different voltage supplies to a common node. A first of the voltage supplies is coupled to the common node by a first switch and a second of the voltage supplies is coupled to the common node by a second switch. The switching device includes the following elements. A difference detector detects a difference between the first and second voltage supplies. A control circuit selectively enables one of the first and second switches and disables the other of the first and second switches, for switching between the first and second voltage supplies in response to the difference detector. The control circuit performs the switching between the first and second voltage supplies when the detected difference falls below a predetermined threshold.