An electronic switching system, comprising a common source of voltage to a plurality of user stations connected in parallel, an electronic means of connection to electrically connect a chosen user station to the common source of voltage, and a means of disconnection command with an optical coupler to control automatically the electronic disconnection of other user stations to the common source of voltage. A default user station is normally the chosen user station. There are means of separation of grounds for the chosen user station and the other user stations. In a preferred embodiment there is a cell for each user station, with each cell including in series a means for separation of the grounds, a means for electrically connecting terminals of the chosen station at boundaries of the source of voltage, a means for filtering a signal and for rectification of alternating current, a means for determination of a response time of the cell, and a means for command of disconnection including optical couplers to control the electronic disconnection of the source of the voltage to the other cells. The optical couplers preferably include a light emitting diode and a light receiving transistor. The optical couplers may be connected in series or in parallel. Preferably, response time is determined by a circuit in each cell containing at least one resistor and at least one capacitor.