. Radiography and radio-therapeutics . n the High each buttonincreases it 16 volts. It is thus possible to get: Button. Low. High. 1 ! 220 220 1 2 204 236 3 188 252 4 172 268 5 156 284 6 140 300 This gives a range of voltage as follows Button. Primary Voltage. Secondary Voltage. 6 140 45,000 5 156 53,000 4 172 61,000 3 188 69,000 2 204 77,000 1 220 85,000 1 220 85,000 2 236 93,000 3 252 101,000 4 268 109,000 5 284 117,000 6 300 125,000 APPARATUS FOE TIME AND RAPID RADIOGRAPHY 45 Because an inductive rheostat is not used, increasing the quantity ofcurrent passing does not increase the voltage v
. Radiography and radio-therapeutics . n the High each buttonincreases it 16 volts. It is thus possible to get: Button. Low. High. 1 ! 220 220 1 2 204 236 3 188 252 4 172 268 5 156 284 6 140 300 This gives a range of voltage as follows Button. Primary Voltage. Secondary Voltage. 6 140 45,000 5 156 53,000 4 172 61,000 3 188 69,000 2 204 77,000 1 220 85,000 1 220 85,000 2 236 93,000 3 252 101,000 4 268 109,000 5 284 117,000 6 300 125,000 APPARATUS FOE TIME AND RAPID RADIOGRAPHY 45 Because an inductive rheostat is not used, increasing the quantity ofcurrent passing does not increase the voltage very much, therefore anyquantity can be obtained at any desired voltage. This type of machinepossesses advantages over other types and should be especially useful whenthe Coolidge tube is used. The Snook apparatus was the first interrupterless machine made ma practical form for X-ray work, and was first introduced and made in Eng-land in 1907, the credit of this particular design being entirely due toMr. H. Clyde Snook of Fig. 33.—Snook apparatus. (Newton & Wright.) The machine consists essentially of three parts : the motor converter,the high-tension transformer, and the high-tension rectifier or the case of the machine designed to run on continuous current, the partfirst named consists of a motor usually about 4 in size, which rmisfrom the main at about 1500 revolutions per minute. This machine has apair of so-called shp rings, from which can be obtained an alternating current. This alternating current is connected to the primary circuit of thetransformer, through a controlling rheostat, and is raised in electrical pressureor voltage to the necessary tension for X-ray work. This high-tension current is, however, alternating in character whereasfor the production of X-rays it is necessary to have a discharge in one direc-tion only, and the latter is obtained by means of the high-tension rectifier. 46 RADIOGRAPHY This consists of a number of e
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