It uses the 2.4 ghz spectrum to communicate a 1 megabit connection between 2 devices for both a voice channel and a 768k data channel. out-of-band signaling), blue boxes no longer work.Ī wireless protocol that is used to communicate from one device to another in a small area usually less than 30 feet. With the advent of CCIS, Common Channel Interoffice Signaling (i.e. No, The Snark and Captain Crunch, who got his name from the free 2600 Hz whistle included as a promotion in boxes of Captain Crunch breakfast cereal. People who used blue boxes in their salad days included characters with adopted pseudonyms like Dr. When they were young, Steve Jobs and Steve Wozniak, founders of Apple Computer, sold blue boxes, which Wozniak built. The first blue box was " discovered " at MIT in a small utility box that was painted blue, thus the term blue box. They are different from those emitted by normal telephones. The tones duplicated the tones which the touchtone pads of long distance operators emitted. The phone network heard those tones and sent the call according to the instructions in the tones. The user then punched in a series of digits on the touchtone pad. This disconnected the ringing at the other end but left the user inside the long distance network. That button caused the blue box's speaker to emit a 2600 Hz tone. While the distant number was ringing, you punched the single button on the top of the blue box. Typically, you went to a coin phone and dialed an 800 number. It had a touchtone pad on the front and a single button on top. The classic blue box was slightly larger than a cigarette container. One defines it strictly in terms of switching capability and ignores the fact that his PBX might not have sufficient other "things," like devices which ring bells on phones (to indicate an incoming call) or devices which deliver dial tone to a phone (to indicate the PBX is ready to receive instructions).Ī device used to steal long distance phone calls. Third, most manufacturers define "non-blocking" differently. Second, a true non-blocking PBX can be very expensive, perhaps too much power and too much money for most peoples' needs. There are several flaws in this logic: First, it's not logical or useful to buy a non-blocking PBX if the chances of being blocked elsewhere ” the local lines, the local exchange or the long distance network ” are very high. " This means it will not, they claim, block a call in the switch. "Blocking" used to be a technical term but has now become a sales tool especially among PBX manufacturers, who increasingly claim their switch to be " non-blocking. Grade of Service is written as P.05 (five percent blocking). It varies from almost zero (best, but most expensive case, no calls blocked) to one (worst case, all calls blocked). The "Grade of Service" is a measurement of blocking. This doesn't work in business, and especially not in telephony. They practice the sales "theory" of selling better service for less money. Many network salesmen, however, don't believe this. Most companies are willing to pay more for better service if someone explains the logic of telephone design to them. Thus, in any telecommunications network design there is always a trade-off: What are you prepared to pay, compared to what can you tolerate ?Įveryone designs their network with different trade-offs depending on what they and their users or customers, can tolerate and/or are willing to pay. We keep adding extra circuits and extra equipment. But as one designs a switching and transmission network for less and less blocking, the network becomes more and more expensive. Less blockage, fewer busies and less frustration. From the user's point of view, the answer is obviously YES, it is better. One might think the fewer blocked calls, the better. This is because numbers that are busy are not the fault of the telephone switching and transmission network. Blocked calls are different from calls that are not completed because the called number is busy. The number of calls you try compared to the number of times you get blocked measures "the grade of service" on that network. Blocking happens because switching or transmission capacity is not available at that precise time. When a telephone call cannot be completed it is said that the call is "blocked." Blocking is a fancy way to say that the caller is "receiving a busy." There are many places a call can be blocked: at the user's own telephone switch ” PBX or key system, at the user's local central office or in the long distance network.
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