A loop line or loop around is a telephone company test circuit. The circuit has two associated phone numbers. When one side of the loop is called (side A), the caller receives a test tone of approximately 1000 Hz ( milliwatt test ). When the second number (side B) is called, it produces dead silence, but the party on side A hears the milliwatt test tone drop, and is connected to the person on side B. The purpose of the loop around test is to allow circuit testing to a distant central office without needing a person at the far end. The technician can send a tone down either line and measure the response tone on the second line to determine the path loss parameters.
5-610: (Redirected from Loop Line ) [REDACTED] Look up loop line in Wiktionary, the free dictionary. Loop line could refer to: Uses in communications and circuits [ edit ] Loop around , telephone company test circuit Loopback , electrical or datacomm loop Uses in transportation [ edit ] Loop line (railway) Loop Line, Chongqing Rail Transit , Chongqing, China See also [ edit ] Circle Line (disambiguation) Topics referred to by
10-438: Is different from Wikidata All article disambiguation pages All disambiguation pages Loop around When a line is connected to side A, multiple telephone lines, within limits, may connect to side B and thus be connected into a conference with the person on side A. The function of the tone on side A was to alert those already connected, when somebody called the B side and connected. Teenagers discovered that
15-415: The same term [REDACTED] This disambiguation page lists articles associated with the title Loop line . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Loop_line&oldid=1147396082 " Category : Disambiguation pages Hidden categories: Short description
20-407: The start of the 21st century. One such loop line is certain to exist: it is a TPI-560P located at (416) 981-0001 owned by Telus. It also comes with an automatic number announcement circuit . Because of the potential for abuse, however, telephone companies seek to protect them. The most common protection techniques are: Eventually, telephone companies designed devices to prevent this misuse of
25-400: The test facility could be used as so-called beep lines , in which they would dial up the primary number and wait for someone at random to call its mate. Phreaks would use the loop around in a similar manner, to exchange information that they had learned about the phone company. Loop lines are far less common today than they were in the 1960s, however they reportedly continued to exist past
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