The Educational screen (c1922-c1956])

Page 322 Educational Screen The ABCs of AudioVisual Equipment Survey Review of 16mm Sound Equipment, „o„cot r crSpSic,? Fresent Use, and Future Needs THE survey forms printed in the April issue have 7. — Interest in purchasing lozv priced ($250.00) equip been returned from a number of individual schools tnent having their specifications as indicated : and school systems across the country. Reader use of 707r of the schools reporting evinced an interest and preference for certain kinds of equipment are far in such equijmient, indicating that from 1-10 from startling in view of the apparatus currently in use such machines might be secured during the and the personnel operating it. The editor, having been next 12 months if available, or an average of directly or in-directly stimulated from various quarters 2.5 machines per school, with respect to the extreme weight, liigii cost, and com Similar equipment surveys will be undertaken from plexity of current motion picture equipment, decided time to time. If you, as readers, feel that additional im that it would be a good idea to secure a consensus of portant information has not been asked for in the pres opinion from you, the readers of the ABC's Department, ent survey and should be included in the future, drop with respect to these various matters. Now, you have the editor a line. These columns are for YOUR infor spoken, and here are the results : mation. 1. — Amount of equipment and age: DeVry Comments on Projector Parade Number of projectors per school 3>4. 6tTT seems that vour addenda in the March "ProProjectors less than a year old, 21%; 1-2 years. 1 jector Parade" stating that tlie amplifier and 28% ; 3-4, 15% ; 5-5, 16%' ; 7-8, 9% ; 9-10, speaker ratings were not absolute factors of comparing 1^^ equipment performance has . . . not been read . . . and 2.— Type of use made of equipment: that much confusion exists as to why the various manu Auditorium only 5% facturers utilizing the same essential tube complement Classroom only 20% have different power output ratings for their ampli Both Classroom and Auditorium 75%^ fiers. 3.— Type of personnel operating equipment and hours "To amplify on the preceding, I should like to pre of training given : sent you with an analysis of methods of rating ampli 807. of schools report use students, who receive fiers. as taken from standard practice, some of which from 1-100 hours of training with an average has been reduced to generally accepted specifications: of 10.8 hours per student. 1.— Power rated at a single frequency usually 400 50% of schools report use of teachers, who receive cycles with 10% distortion. from 15 minutes to three hours of training. 2.— Academy of Motion Picture Arts & Sciences— with an average of 1.7 hours each. power rated at all frequencies for which the equip 5% of schools report use of other paid help, who nient is usable at less than 2% distortion. receive 4 hours of instruction each. 3.— Navy— power rated at a single frequency at less 4.— Most satisfactory operating personnel : than 6% distortion. SO'/r have found students most satisfactory and 4.— Joint Army-Navy specification P-49 and U. S. intend to continue using them. Treasun Dept. specification— power rated at lO'Yc have found teachers most satisfactory and less than 2% from 100 to 2000 cycles and less intend to continue using this type of person than 4% from 2000 to 4000 cycles' "^' "Now, as you can see from the preceding, the same 5.— Personnel used to move equipment from room to amplifier is capable of several power ratings— for ex rooin : ample, the amplifier listed in vour rating as measured Students 65%; Teachers 25%, Janitors 5%. y^jgr Method 1, develops 32 watts, whereas under Other paid help 5%. Method 2, develops 18 watts, and for complete com 6.— Characteristics insisted upon as ideal equipment: parison. develops 29 watts under Method 3, and 26 Briefly, those schools reporting mentioned most watts under Method 4. frequently 1000 watt illumination, sound and ..^u ^f j^e preceding adds up to mean that you cansilent operating speeds, sufficient volume for ^^^ evaluate an amplifier on a wattage basis without classroom and auditorium use, and motor rewind. specifying the per cent distortion and the method of A detailed breakdown of specific items by per measurement." e. W. D'ARCY, DeVry Corporation centages of schools follows; ,. , », t^ i ^ , • Editor s Note : — Readers of this department, having Lamps: 1000 watt 60% Weiglit : 50-75 lbs. 30% negotiated the foregoing, may well understand that the 500 or less 5% 25 or less 20% Editor's major concern in preparing "Projector Par „ J ■ , .,A« Blimp case 50% ade" was to present a lucid, usal)le account for the Speeds: sd. only . 20% ,,. , , ..L , , • ,, r • . , ■ • ■ jj^ gQ^ Microphone attachment 55% average purchaser, technically safeguarded by stating m reverse 20% '^'^'°'" '"'^wind 80% tj^g article that "Amplifier rated output and speaker .-.1 -v^X/ Micrometer tilt 50% ^ i -.^ • ^^ still 20% ^ -CM rated capacity in watts are not an exact measure ot useOne case 25% -i ui >• tti . • i Volume: classroom 20% Two cases 45% i"' power available. . . . hlectrical engineers in our auditorium 80% Special safety devices 35% ranks will appreciate Mr. D'Arcy's helpful clarification.