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(詳細はtelecommunications, in-band signaling is the sending of metadata and control information within the same band or channel used for voice (e.g. DTMF tones) and can be heard by the callers, as opposed to out-of-band signals (e.g. SS7 control signals) which cannot be heard as they are on a different channel or band. ==Telephone== For example, when dialing from a land-line telephone, the telephone number is encoded and transmitted across the telephone line in form of dual-tone multi-frequency signaling (DTMF). The tones control the telephone system by instructing the telephone switch where to route the call. These control tones are sent over the same channel and in the frequency range (300Hz to 3.4kHz) as the audio of the telephone call. In-band signaling is also used on older telephone carrier systems to provide inter-exchange information for routing calls. Examples of this kind of in-band signaling system are SS5 and R2. Separating the control signals, also referred to as the control plane, from the data (if a bit-transparent connection is desired) is usually done by escaping the control instructions. Occasionally, however, networks are designed so that data is (to a varying degree) garbled by the signaling. Allowing data to become garbled is usually acceptable when transmitting sounds between humans, since the users rarely notice the slight degradation, but this leads to problems when sending data that has very low error tolerance, such as information transmitted using a modem. In-band signaling is insecure because it exposes control signals, protocols and management systems to end users, which may result in falsing. In the 1960s and 1970s, some individuals, referred to as ''phone phreaks'', used blue boxes for deliberate falsing, in which the appropriate tones for routing were intentionally generated, enabling the caller to abuse functions intended for testing and administrative use and to make free long-distance calls. Modems may also interfere with in-band signaling, so in some countries, a guard tone is employed to prevent this. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「In-band signaling」の詳細全文を読む スポンサード リンク
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