Arrangement comprising a switchable longitudinal voltage source and a polarity reversal device, wherein the longitudinal voltage source has a feed-in terminal for feeding in a current, a first output terminal and a second output terminal, wherein the longitudinal voltage source is suitable for optionally switching an electrical voltage of an electrical energy store between the feed-in terminal and the first output terminal or between the feed-in terminal and the second output terminal, wherein - the longitudinal voltage source has a first switch, which is situated electrically between the feed-in terminal and the first output terminal, electrically connects the feed-in terminal and the first output terminal in the switched-on state and electrically disconnects the feed-in terminal and the first output terminal from one another in the switched-off state, - the longitudinal voltage source has a second switch, which is situated electrically between the feed-in terminal and the second output terminal, electrically connects the feed-in terminal and the second output terminal in the switched-on state and electrically disconnects the feed-in terminal and the second output terminal from one another in the switched-off state, - the longitudinal voltage source has a third swich, which is situated electrically in series with the energy store and forms a series circuit therewith, said series circuit being electrically connected between the two output terminals (B, C), and - the polarity reversal device is connected between the two output terminals (B, C) of the longitudinal voltage source and two conductor terminal contacts (30a, 30b) of the polarity reversal device, wherein in a first position the polarity reversal device connects the first output terminal to the first conductor terminal contact and the second output terminal to the second conductor terminal contact, and wherein in a second position the polarity reversal device connects the first output terminal to the second conductor terminal contact and the second output terminal to the first conductor terminal contact. - the longitudinal voltage source has a first switch, which is situated electrically between the feed-in terminal and the first output terminal, electrically connects the feed-in terminal and the first output terminal in the switched-on state and electrically disconnects the feed-in terminal and the first output terminal from one another in the switched-off state, - the longitudinal voltage source has a second switch, which is situated electrically between the feed-in terminal and the second output terminal, electrically connects the feed-in terminal and the second output terminal in the switched-on state and electrically disconnects the feed-in terminal and the second output terminal from one another in the switched-off state, - the longitudinal voltage source has a third swich, which is situated electrically in series with the energy store and forms a series circuit therewith, said series circuit being electrically connected between the two output terminals (B, C), and - the polarity reversal device is connected between the two output terminals (B, C) of the longitudinal voltage source and two conductor terminal contacts (30a, 30b) of the polarity reversal device, wherein in a first position the polarity reversal device connects the first output terminal to the first conductor terminal contact and the second output terminal to the second conductor terminal contact, and wherein in a second position the polarity reversal device connects the first output terminal to the second conductor terminal contact and the second output terminal to the first conductor terminal contact.