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Machine vision systems often require bright and homogeneous illumination, so features of interest are easier to process. LEDs are often used for this purpose, and this is likely to remain one of their major uses until the price drops low enough to make signaling and illumination uses more widespread. Barcode scanners are the most common example of machine vision, and many low cost products use red LEDs instead of lasers. Optical computer mice are an example of LEDs in machine vision, as it is used to provide an even light source on the surface for the miniature camera within the mouse. LEDs constitute a nearly ideal light source for machine vision systems for several reasons:

LEDs are often used for what type of systems?
Answer: Machine vision
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iPods cannot play music files from competing music stores that use rival-DRM technologies like Microsoft's protected WMA or RealNetworks' Helix DRM. Example stores include Napster and MSN Music. RealNetworks claims that Apple is creating problems for itself by using FairPlay to lock users into using the iTunes Store. Steve Jobs stated that Apple makes little profit from song sales, although Apple uses the store to promote iPod sales. However, iPods can also play music files from online stores that do not use DRM, such as eMusic or Amie Street.

The iPod can play music from other online stores as long as they don't contain what feature?
Answer: DRM
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Prior to the second world war, birth control was prohibited in many countries, and in the United States even the discussion of contraceptive methods sometimes led to prosecution under Comstock laws. The history of the development of oral contraceptives is thus closely tied to the birth control movement and the efforts of activists Margaret Sanger, Mary Dennett, and Emma Goldman. Based on fundamental research performed by Gregory Pincus and synthetic methods for progesterone developed by Carl Djerassi at Syntex and by Frank Colton at G.D. Searle & Co., the first oral contraceptive, Enovid, was developed by E.D. Searle and Co. and approved by the FDA in 1960. The original formulation incorporated vastly excessive doses of hormones, and caused severe side effects. Nonetheless, by 1962, 1.2 million American women were on the pill, and by 1965 the number had increased to 6.5 million. The availability of a convenient form of temporary contraceptive led to dramatic changes in social mores including expanding the range of lifestyle options available to women, reducing the reliance of women on men for contraceptive practice, encouraging the delay of marriage, and increasing pre-marital co-habitation.

What law prohibited birth control?
Answer:
Comstock laws