the men's SS, but in contrast it was only confined to voluntary work in Emergency Service (Notdienstverpflichtung). SS Women belonged either to the SS-Helferinnen (de) or the SS-Kriegshelferinnen. They were in charge of auxiliary transmissions (telephone, radio operators, stenographers) in the SS and sometimes in camps (these were the Aufseherin, see next section). There was an internal hierarchy in the women's wing of the SS, which had no influence on the male troops, although the titles designated to the women sometimes had an influence upon the owners. However, whereas female camp guards were civilian employees of the SS, the SS-Helferinnen who completed training at the Reich-school in Obernai (Oberehnheim) were members of the Waffen-SS. The SS-Helferinnen were trained at the Reichsschule-SS at Oberehnheim in Alsace. The Reichsschule-SS (in full, the Reichsschule für SS Helferinnen Oberenheim) was the training centre for the SS, reserved for women, and opened in Obernai in May 1942 upon the order of Heinrich Himmler. The SS-Helferinnenkorps has also been termed by historians as the 'SS-Frauenkorps'. 7,900 women were employed in the clerical unit of the SS, the SS Frauenkorps, and 10,000 as SS auxiliaries or Helferinnen. The training was more difficult than that for women enrolled in the German Army. They had to meet certain physical criteria determined by the regime: they must be aged 17 to 30 years and measure more than tall, while over the long term, the enrollment criteria were relaxed (the age limit was raised to 40 years and minimum height dropped to 1.58 metres); they even accepted 15 Muslim students. Having been in a privileged status, war widows were favoured before the admissions were opened up to other social classes. Women enrolled at the Reichsschule-SS came from various economic, class and educational backgrounds and included a member of the aristocracy in the ranks, Princess Ingeborg Alix. The Reichsschule-SS appealed to female Nazi ideologues who foresaw the possibility of social ascent by becoming an SS-Helferin, and candidates were often from families with other SS and NSDAP members. It has been noted by historians that "some SS-Helferinnen knew about the persecution of those whom the Nazis deemed to be worthless; Hermine S., who worked as an administrator at Auschwitz, stated that she knew the word Sonderbehandlung meant the gassing of prisoners." In her review of Jutta Muhlenberg's book, Das SS-Helferinnenkorps: Ausbildung, Einsatz und Entnazifizierung der weiblichen Angehörigen der Waffen-SS 1942–1949, Rachel Century writes: