. The Bell System technical journal . Fig. 4—Sertion of disc with lens system for utilizing small area light Fig. 5—Disc with condensing lenses as used at the receiving ends of two-way tele-vision system. 272 BELL SYSTEM TECHNICAL JOURNAL entire frame of the picture and the lenses /; P represents the glow lampelectrode. A great advantage of this optical arrangement is that thecathode of the glow lamp can be made quite small, and can be removed,as shown, to a considerable distance from the glass wall of the contain-ing tube. In consequence of these changes in lamp design, a very highcu
. The Bell System technical journal . Fig. 4—Sertion of disc with lens system for utilizing small area light Fig. 5—Disc with condensing lenses as used at the receiving ends of two-way tele-vision system. 272 BELL SYSTEM TECHNICAL JOURNAL entire frame of the picture and the lenses /; P represents the glow lampelectrode. A great advantage of this optical arrangement is that thecathode of the glow lamp can be made quite small, and can be removed,as shown, to a considerable distance from the glass wall of the contain-ing tube. In consequence of these changes in lamp design, a very highcurrent density can be obtained for a relatively low expenditure ofenergy, with at the same time a long lamp life. The condenser lens disc is observed exactly as the simple disc, bythe eye placed at E. According to Nipkow, when lenses are used onthe disc, the holes should be covered with diffusing material. This isnot necessary in the present case, because in the two-way booth, theobserver has very little latitude of motion, and it is only necessary thathis eyes lie in the overlapping cones of rays from the extr
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
