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The Mark Tabas encounter series presents:-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Better Homes and Blue Boxing Part I Theory of Operation=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- To quote Karl Marx, blue boxing hasalways been the mst oble form ofphreaking. As opposed to such thingsas using an MCI code to make a freefone call, which is merely mindlesspseudo-phreaking, blue boxing isactual interaction with the BellSystem toll network. It is likewiseadvisable to be more cautious whenblue boxing, but the careful phreakwill not be caught, regardless of whattype of switching system he is under. In this part, I will explain how andwhy blue boxing works, as well aswhere. In later parts, I will givemore practical information for blueboxing and routing information. To begin with, blue boxing is simplycommunicating with trunks. Trunks mustnot be confused with subscriber lines(or "customer loops") which arestandard telefone lines. Trunks arethose lines that connect centraloffices. Now, when trunks are not inuse (i.e., idle or "on-hook" state)they have 2600Hz applied to them. Ifthey are two-way trunks, there is2600Hz in both directions. When atrunk IS in use (busy or "off-hook"state"), the 2600Hz is removed fromthe side that is off-hook. The 2600Hzis therefore known as a supervisorysignal, because it indicates thestatus of a trunk; on hook (tone) oroff-hook (no tone). Note also that2600Hz denoted SF (single frequency)signalling and is "in-band." This isvery important. "In-band" means thatis is within the band of frequenciesthat may be transmitted over normaltelefone lines. Other SF signals, suchas 3700Hz are used also. However, theycannot be carried over the telefonenetwork normally (they are "out-of-band") and are therefore not able tobe taken advantage of as 2600Hz is. Back to trunks. Let's take ahypothetical phone call. You pick upyour fone and dial 1+806-258-1234(your good friend in Armarillo,Texas). For ease, we'll assume thatyou are on #5 Crossbar switching andnot in the 806 area. Your centraloffice (CO) would recognize that806 is a foreign NPA, so it wouldroute the call to the toll centrethat serves you. [For the sake ofaccuracy here, and for the moreexperienced readers, note that theCO in question is a class 5 withLAMA that uses out-of-band SFsupervisory signalling]. Dependingon where you are in the country, thecall would leave your toll centre(on more trunks) to another tollcentre, or office of higher "rank".Then it would be routed to centraloffice 806-258 eventually and thecall would be completed. Illustration:A---CO1-------TC1------TC2----CO2----BA=you CO1=your central officeTC1=your toll office. TC2=toll office in Amarillo.CO2=806-258 central office. B=your friend (806-258-1234) In this situation it would berealistic to say that CO2 uses SFin-band (2600Hz) signalling, whileall the others use out-of-bandsignalling (3700Hz). If you don'tunderstand this, don't worry too much.I am pointing this out merely for thesake of accuracy. The point is thatwhile you are connected to 806-258-1234, all those trunks from YOURcentral office (CO1) to the 806-258central office (CO2) do *NOT* have2600Hz on them, indicating to theBell equipment that a call is inprogress and the trunks are in use. Now let's say you're tired oftalking to your friend in Amarillo(806-258-1234) so you send a 2600Hzdown the line. This tone travels downthe line to your friend's centraloffice (CO2) where it is detected.However, that CO thinks that the2600Hz is originating from Bellequipment, indicating to it thatyou've hung up, and thus the trunksare once again idle (with 2600Hzpresent on them). But actually, youhave not hung up, you have fooled theequipment at your friend's CO intothinking you have. Thus,it disconnectshim and resets the equipment toprepare for the next call. All thishappens very quickly (300-800ms forstep-by-step equipment and 150-400ms for other equipment). When you stop sending 2600Hz (afterabout a second), the equipment thinksthat another call is coming towardsit (e.g. it thinks the far end hascome "o
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