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Journey of Cables – From Coppers to Optical Fiber
Published in Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez, Network Evolution and Applications, 2023
Vikas Kumar Jha, Bishwajeet Pandey, Ciro Rodriguez Rodriguez
The initial telephone lines and the voice-grade signals were totally analog signals and were carried through the electrical cables (copper wires) in the form of electrical signals. The continuous variation in signal amplitude and frequency characterizes an analog signal. When we speak into a handset, the air pressure around our mouth changes with our voice in the case of telephony. Those changes in the air pressure fall onto the microphone of the handset, which then amplify and get converted into an electrical signal as current or voltage fluctuations. This signal conversion from voice to current fluctuations is analog in characteristic and represents the actual voice pattern. The speech frequency range of the vast majority of intelligible sounds falls between 250 and 3,400 Hz, and therefore, a total bandwidth of 4,000 Hz was typically allotted for voice transmission by the telephone companies. However, the twisted-pair wire has a total capacity of 1 MHz of the frequency spectrum. Due to this reason, there was a requirement of putting a bandwidth-limiting filter on the analog circuit to filter out all frequencies above 4,000 Hz to provision a voice-grade analog circuit. Because of that, the analog circuits can conduct only low-speed data communications, and the maximum data rate over an analog facility is 33.6 Kbps [7].
Home Automation in Cloud-Based IoT
Published in Fadi Al-Turjman, The Cloud in IoT-enabled Spaces, 2019
Fadi Al-Turjman, Mohamad Sanwal
Digital subscriber line (DSL) technology is a wired communication medium that transfers data through the standard telephone lines at a frequency range of 4,000 Hz to 4 MHz depending on the type. The technology is approved by ITU G.992 recommendations. Three different types of this technology are commonly used: Asymmetric DSL (ADSL) offers a data rate of 1–8 Mbps with a maximum coverage of 5 km, high bit-rate DSL (HDSL) provides a data rate of 2 Mbps for a distance of 3.6 km, and very high-speed DSL (VDSL) can cover a maximum of 1.5 km distance but with relatively higher data rates that range between 15 and 100 Mbps. Unlike ADSL, the key feature associated with HDSL type is the symmetricity of downstream and upstream where it processes an equal data packet in both directions. DSL technologies can be integrated with IoT-based smart homes’ HANs and NANs. They can also provide access to rural areas and distribution and transmission substations.
Internet Applications
Published in Akshi Kumar, Web Technology, 2018
Internet Telephony is the service provided by the Internet that uses the Voice over Internet Protocol (VoIP) application layer protocol in the TCP/IP protocol stack to offer this service. It is the technology that is used to transmit voice over the Internet. The voice is first converted into digital data, which is then organized into small packets. These packets are stamped with the destination IP address and routed over the Internet. At the receiving end, the digital data is reconverted into voice and fed into the user’s phone. VoIP is a form of communication that allows you to make phone calls over a broadband Internet connection instead of typical analog telephone lines. Basic VoIP access usually allows you to call others who are also receiving calls over the Internet. Some VoIP services require a computer or a dedicated VoIP phone, while others allow you to use your landline phone to place VoIP calls through a special adapter. Thus, for VoIP, you need a broadband Internet connection, plus a traditional phone and an adapter; a VoIP-enabled phone; or VoIP software on your computer. VoIP examples include Xbox Voice, Windows messenger, AOL Instant Messenger, Motorola Phone Adapter (Vonage), Cisco Phone, and Skype (Figure 2.5).
Concurrent Solar-Illumination and Power Line Voice Communication for Indian Underground Coal Mines – An Experimental Study
Published in IETE Journal of Research, 2022
R. N. Raul, T. Maity, S. Palit
The load end voltages in case of both the modes indicate the voltage drops in the circuits. The impedance of a telephone, when off-hook, will drop the voltage from supply to the recorded level across the telephone line. In the experimental model two telephone sets are considered to fulfil the minimum number required to establish any voice communication. These sets may be placed at two end locations in the system. Initially there is no current through the communication path. A small current of around 0.04 A flows through during the working of telephone sets in talking state. This results in a small hike in the line current as compared to the idle state, which marginally increases the power consumption as well.