Problem: A few lines of the Paris Metro in France operate on a four-rail power scheme because they run on rubber tyres which run on a pair of narrow roadways made of steel and, in some places, concrete. Since the tyres do not conduct the return current, the two guide rails provided outside the running 'roadways' double up as conductor rails, so at least electrically it is a four-rail scheme. One of the guide rails is bonded to the return conventional running rails situated inside the roadway so a single polarity supply is required. The trains are designed to operate from either polarity of supply, because some lines use reversing loops at one end, causing the train to be reversed during every complete journey. The loop was originally provided to save the original steam locomotives having to 'run around' the rest of the train saving much time. Today, the driver does not have to change ends at termini provided with such a loop, but the time saving is not so significant as it takes almost as long to drive round the loop as it does to change ends. Many of the original loops have been lost as lines were extended.
How train is able to turn around after each completed journey?
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Answer: reversing loops

Problem: Washington University's North Campus and West Campus principally house administrative functions that are not student focused. North Campus lies in St. Louis City near the Delmar Loop. The University acquired the building and adjacent property in 2004, formerly home to the Angelica Uniform Factory. Several University administrative departments are located at the North Campus location, including offices for Quadrangle Housing, Accounting and Treasury Services, Parking and Transportation Services, Army ROTC, and Network Technology Services. The North Campus location also provides off-site storage space for the Performing Arts Department. Renovations are still ongoing; recent additions to the North Campus space include a small eatery operated by Bon Appetit Management Company, the University's on-campus food provider, completed during spring semester 2007, as well as the Family Learning Center, operated by Bright Horizons and opened in September 2010.
When was the building and property for the north campus of Washington University acquired?
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Answer: 2004

Problem: The mid-1970s saw the introduction of dbx-encoded records, again for the audiophile niche market. These were completely incompatible with standard record playback preamplifiers, relying on the dbx compandor encoding/decoding scheme to greatly increase dynamic range (dbx encoded disks were recorded with the dynamic range compressed by a factor of two in dB: quiet sounds were meant to be played back at low gain and loud sounds were meant to be played back at high gain, via automatic gain control in the playback equipment; this reduced the effect of surface noise on quiet passages). A similar and very short-lived scheme involved using the CBS-developed "CX" noise reduction encoding/decoding scheme.
What did CBS develop in order to reduce outside noise?
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Answer:
"CX" noise reduction