To quote Karl Marx, blue boxing has always been the most noble form of phreaking. As opposed to such things as using an MCI code to make a free fone call, which is merely mindless pseudo-phreaking, blue boxing is actual interaction with the Bell System toll network. It is likewise advisable to be more cautious when blue boxing, but the careful phreak will not be caught, regardless of what type of switching system he is under. In this part, I will explain how and why blue boxing works, as well as where. In later parts, I will give more practical information for blue boxing and routing information. To begin with, blue boxing is simply communicating with trunks. Trunks must not be confused with subscriber lines (or “customer loops”) which are standard telefone lines. Trunks are those lines that connect central offices. Now, when trunks are not in use (i.e., idle or “on-hook” state) they have 2600Hz applied to them. If they are two-way trunks, there is 2600Hz in both directions. When a trunk IS in use (busy or “off-hook” state), the 2600Hz is removed from the side that is off-hook. The 2600Hz is therefore known as a supervisory signal, because it indicates the status of a trunk; on hook (tone) or off-hook (no tone). Note also that 2600Hz denoted SF (single frequency) signalling and is “in-band.” This is very important. “In-band” means that is within the band of frequencies that may be transmitted over normal telefone lines. Other SF signals, such as 3700Hz are used also. However, they cannot be carried over the telefone network normally (they are “out-of-band” and are therefore not able to be taken advantage of as 2600Hz is. Back to trunks. Let’s take a hypothetical phone call. You pick up your fone and dial 1+806-258-1234 (your good friend in Amarillo, Texas). For ease, we’ll assume that you are on #5 Crossbar switching and not in the 806 area. Your central office (CO) would recognize that 806 is a foreign NPA, so it would route the call to the toll centre that serves you. [For the sake of accuracy here, and for the more experienced readers, note that the CO in question is a class 5 with LAMA that uses out-of-band SF supervisory signalling]. Depending on where you are in the country, the call would leave your toll centre (on more trunks) to another toll centre, or office of higher “rank”. Then it would be routed to central office 806-258 eventually and the call would be completed. IllustrationA—CO1——-TC1——TC2—-CO2—-BA…. youCO1=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 be realistic to say that CO2 uses SFin-band (2600Hz) signalling, while all the others use out-of-band signalling (3700Hz). If you don’t understand this, don’t worry. I am pointing this out merely for the sake of accuracy. The point is that while you are connected to 806-258-1234, all those trunks from YOUR central office (CO1) to the 806-258 central office (CO2) do *NOT* have 2600Hz on them, indicating to the Bell equipment that a call is in progress and the trunks are in use. Now let’s say you’re tired of talking to your friend in Amarillo, so you send a 2600Hz down the line. This tone travels down the line to your friend’s central office (CO2) where it is detected. However, that CO thinks that the 2600Hz is originating from Bell equipment, indicating to it that you’ve hung up, and thus the trunks are once again idle (with 2600Hz present on them). But actually, you have not hung up, you have fooled the equipment atyour friend’s CO into thinking you have. Thus,it disconnects him and resets the equipment to prepare for the next call. All this happens very quickly (300-800ms for step-by-step equipment and 150-400ms for other equipment). When you stop sending 2600Hz (after about a second), the equipment thinks that another call is coming towards –> on hook, no tone –>off hook.
Now that you’ve stopped sending 2600Hz, several things happen:1) A trunk is seized.2) A “wink” is sent to the CALLING end from the CALLED end indicating that the CALLED end (trunk) is not ready to receive digits yet.3) A register is found and attached to the CALLED end of the trunk within about two seconds (max).4) A start-dial signal is sent to the CALLING end from the CALLED end indicating that the CALLED end is ready to receive digits.
Now, all of this is pretty much transparent to the blue boxer. All hereally hears when these four things happen is a