Lamp Tester AI 990 The lamp test device AI 990 includes a group of diodes with common anode. The diodes make sure that the different lamps do not influence each other. Because of this diode circuit the lamp only shows half intensity when operated with AC voltage. Features . For max. 19 signal lamps . Width: 45 mm Technical specifications Width: 45mm Enclosure design: Switch cabinet Type: AI 990 Manufacturer: E. Dold & Söhne GmbH & Co. KG Type: AI 990 Art. No.: 0002060