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SEADS Region shown in NORAD Region/Sector Configuration, 1987-2005 Historical map of Montgomery Air Defense Sector, 1957-1966. The Southeast Air Defense Sector (SEADS), was a unit of the US Air Force located at Tyndall Air Force Base near Panama City, Florida. It provided air defense and surveillance of the southeastern region of the US.
The "nine dots" puzzle. The puzzle asks to link all nine dots using four straight lines or fewer, without lifting the pen. The nine dots puzzle is a mathematical puzzle whose task is to connect nine squarely arranged points with a pen by four (or fewer) straight lines without lifting the pen or retracing any lines.
In telephony a four-wire circuit was historically used to transport and switch baseband audio signals in the phone company telephone exchange before the advent of digital modulation and the electronic switching system eliminated baseband audio from the telco plant except for the local loop.
Every two-wire or balanced transmission line has an implicit (or in some cases explicit) third wire which is called the shield, sheath, common, earth, or ground. So every two-wire balanced transmission line has two modes which are nominally called the differential mode and common mode. The circuit shown in the bottom diagram only can model the ...
Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb(C 2 H 5) 4. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 1920s.
Utility pole with electric lines (top) and telephone cables. Fixed telephone lines per 100 inhabitants, 1997–2007. Cross section of telephone cable of 1,800 twisted pairs, 1922. A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. [1]
If a call is delivered to line 1, the next call goes to 2, the next to 3. The succession throughout each of the lines continues even if one of the previous lines becomes free. When the end of the hunt group is reached, the hunting starts over at the first line. Lines are skipped only if they are still busy on a previous call.
Finally, it will come back into the room through the fourth wall and end. If the solution line starts somewhere else, the observer will see the solution line come into and leave his room exactly twice, passing through all four walls in some order. There is no problem with any of this. Consider, however, the observers in the remaining three rooms.