wmartin@brl-tgr.ARPA (Will Martin ) (07/29/85)
The following list of questions was printed in MONITORING TIMES, July '85, page 19. The first person to send correct answers to *all* these queries (to the mailing address given below) will get a free book from those published by Grove. However, I think this is the ideal sort of thing to be discussed on the net, so I thought it might be interesting to throw these out to inspire discussion, debate, and infuriated flamage... Why were phonograph turntable speeds set at 33 1/3rd, 45, and 78 RPM? Why were tape recorder speeds set at 3 3/4ths, 7 1/2, and 15 IPS? Why was motion picture film width set at 8, 16, and 35 mm? Why are the standard worldwide AC line-voltage frequencies 50 or 60 Hz? Why is line voltage typically 120 or 240 Volts? Why are standard US (NTSC) tv pictures composed of 525 lines? Why was 500 kHz chosen as the worldwide marine distress frequency? Why were 50, 72, and 300 ohms selected as standard antenna matching impedances? Why is the commercial motion picture frame rate 24 per second? *** End of question list *** If you want to try to win the book, you can send your answers to: Monitoring Times Grove Enterprises PO Box 98 Brasstown, NC 28902 Myself, I have *no idea* as to the answers to most of these "why?"s -- I think I recall reading the answers to some of them in the past, but cannot recall just where... Happy debate! Will