The switching unit (1) has a switch (2) with a switching contact (5) and an illumination unit (6), and has a control unit connected with the switch. The switching contact and the illumination unit are inserted in a parallel manner and are connected with th...

A glass having a SiO2-Al2O3-B2O3-RO (RO is at least one of MgO, CaO, BaO, SrO and ZnO) based composition, a temperature corresponding to 10 poise being 1570 DEG C or higher and an alkali content of 0.01 to 0.2% and a ZrO2 content of 0.01 to 0.3%, as expres...