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Plain-old Telephone Service
Plain old telephone service (POTS), or publicly offered telephone service, is basic voice-grade telephone service. Historically, POTS has been delivered by analog signal transmission over copper loops, but the term also describes backward-compatible analog connections offered by digital telephone systems. Copper loop POTS was the standard service offering from telephone companies in the United States from 1876 until 1988, when the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) was introduced, followed by the development of cellular telephone systems and voice over internet protocol (VoIP). Despite the advent of these technologies, copper loop POTS remains a basic form of residential and small business connection to the telephone network in many parts of the world. The term encapsulates a technology that has been available since the introduction of the public telephone system in the late 19th century, remaining largely unchanged despite the introduction of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice Band
A voice frequency (VF) or voice band is the range of Audio frequency, audio frequencies used for the transmission (telecommunications), transmission of speech. Frequency band In telephony, the usable human voice, voice frequency band ranges from approximately 300 to 3400 Hertz, Hz. It is for this reason that the ultra low frequency band of the electromagnetic spectrum between 300 and 3000 Hz is also referred to as ''voice frequency'', being the electromagnetic energy that represents acoustic energy at baseband. The Bandwidth (signal processing), bandwidth allocated for a single Voice channel, voice-frequency transmission channel is usually 4 kHz, including guard bands, allowing a sampling rate of 8 kHz to be used as the basis of the pulse-code modulation system used for the digital PSTN. Per the Nyquist–Shannon sampling theorem, the sampling frequency (8 kHz) must be at least twice the highest component of the voice frequency via appropriate filtering ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dual-tone Multi-frequency Signaling
Dual-tone multi-frequency (DTMF) signaling is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and Automatic telephone exchange, switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones, starting in 1963. The DTMF frequencies are standardized in ITU-T Recommendation Q.23. The signaling system is also known as ''MF4'' in the United Kingdom, as ''MFV'' in Germany, and ''Digitone'' in Canada. Touch-tone dialing with a telephone keypad gradually replaced the use of rotary dials and has become the industry standard in telephony to control equipment and signal user intent. The signaling on trunks in the telephone network uses a different type of multi-frequency signaling. Multifrequency signaling Before the development of DTMF, telephone numbers were dialed with rotary dials ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abbreviated Dialing
Abbreviated dialing is the use of a very short digit sequence to reach specific telephone numbers, such as those of public services. The purpose of such numbers is to be universal, short, and easy to remember. Typically they are two or three digits. Carriers refer to the shortened number sequences as ''abbreviated dialing codes'' (ADCs). Unlike SMS short codes, they are generally not automatically synchronized across carriers. ADCs are provisioned separately for mobile networks versus landline networks. Examples The most commonly known examples are emergency telephone numbers such as 9-9-9, 1-1-2 and 9-1-1. Other services may also be available through abbreviated dialing numbers, such as the other of the eight N11 codes of the North American Numbering Plan (NANP) besides 9-1-1. State highway departments in recent years have used abbreviated dialing codes to allow drivers to obtain information about road conditions or to reach the state highway patrol. Examples are *55 in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caller ID
Caller identification (Caller ID) is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is being set up. The caller ID service may include the transmission of a name associated with the calling telephone number, in a service called Calling Name Presentation (CNAM). The service was first defined in 1993 in International Telecommunication UnionTelecommunication Standardization Sector (ITU-T) Recommendation Q.731.3. The information received from the service is displayed on a telephone display screen, on a separately attached device, or on other displays, such as cable television sets when telephone and television service is provided by the same vendor. Value to society includes allowing suicide-prevention hotlines to quickly identify a caller, and enabling businesses (for an example, restaurants and florists) to quickly have co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voicemail
A voicemail system (also known as voice message or voice bank) is a computer-based system that allows callers to leave a recorded message when the recipient has been unable (or unwilling) to answer the phone. Calls may be directed to voicemail manually or automatically. The caller is prompted to leave a message that the recipient can retrieve at a later time. Voicemail can be used for personal calls, but more complex systems exist for companies and services to handle the volume of customer requests. The term is also used more broadly to denote ''any'' system of conveying stored telecommunications voice messages, including using older technology like answering machines. Features Voicemail systems are designed to convey a caller's recorded audio message to a recipient. To do so they contain a user interface to select, play, and manage messages; a delivery method to either play or otherwise deliver the message; and a notification ability to inform the user of a waiting message ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calling Feature
A vertical service code (VSC) is a sequence of digits and the signals star () and pound/hash () dialed on a telephone keypad or rotary dial to access certain telephone service features. Some vertical service codes require dialing of a telephone number after the code sequence. On a touch tone telephone, the codes are usually initiated with the star key, resulting in the commonly used name ''star codes''. On rotary dial telephones, the star is replaced by dialing ''11''. In North American telephony, VSCs were developed by the American Telephone and Telegraph Company (AT&T) as Custom Local Area Signaling Services (CLASS or LASS) codes in the 1960s and 70s. Their use became ubiquitous throughout the 1990s and eventually became a recognized standard. As ''CLASS'' was an AT&T trademark, the term ''vertical service code'' was adopted by the North American Numbering Plan Administration. The use of ''vertical'' is a somewhat dated reference to older switching methods and the fact that t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volt
The volt (symbol: V) is the unit of electric potential, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Units (SI). Definition One volt is defined as the electric potential between two points of a electrical conductor, conducting wire when an electric current of one ampere dissipates one watt of power (physics), power between those points. It can be expressed in terms of SI base units (metre, m, kilogram, kg, second, s, and ampere, A) as : \text = \frac = \frac = \frac = \text\text^2\text^. Equivalently, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can be expressed in terms of SI base units (metre, m, kilogram, kg, second, s, and ampere, A) as : \text = \frac = \frac = \frac = \text\text^2\text^. It can also be expressed as amperes times ohms (curre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Local Loop
In telephony, the local loop (also referred to as the local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common carrier or telecommunications service provider's network. At the edge of the carrier access network in a traditional public telephone network, the local loop terminates in a circuit switch housed in an incumbent local exchange carrier or telephone exchange. Infrastructure Traditionally, the local loop was an electrical circuit in the form of a single pair of conductors from the telephone on the customer's premises to the local telephone exchange. Single-wire earth return lines had been used in some countries until the introduction of electric tramways from the 1900s made them unusable. Historically the first section was often an aerial open-wire line, with several conductors attached to porcelain insulators on cross-arms on "te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tip And Ring
Tip and ring are the two conductors, or sides, of a telephone line. Their names are derived from the telephone plugs used for connecting telephone calls in manual switchboards. One side of the line is connected to the metal ''tip'' of the plug, and the second is connected to a metal ''ring'' behind the tip, separated and insulated from the tip by a non-conducting material. When inserted into a jack, the plug's tip conductor connects first, followed by the ring conductor. In many European countries, tip and ring are referred to as the ''A'' and ''B wires''. Neither of the conductors is permanently connected to earth, but one may be connected to earth during signaling operations. Typically, the ''ring'' conductor has a direct current (DC) potential of to with respect to the tip conductor when the line is in the ''on-hook'' (''idle'') state. ''Floating'' both conductors, i.e. not referencing either one to ground, minimizes the effect of interference from any nearby alternating curr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E And M Signaling
E and M signaling is a type of supervisory line signaling that uses DC signals on separate leads, called the "E" lead and "M" lead, traditionally used in the telecommunications industry between telephone switches. Various mnemonic names have been used to memorize these letters, such as ''Earth'' and ''Magneto'' or ''Ear'' and ''Mouth'', the most common variation. E&M was originally developed for signaling between PABXs in different geographic locations over an analog private circuit. The protocol was later extended for use on digital carrier system with Channel Associated Signaling (CAS). Signaling units and trunk circuits The E&M standards were initially developed by Bell Labs and extended by national PTT administrations. The standard defines two sides of the interface, the trunk circuit and the signaling unit. The trunk circuit is normally the side to which the PABX is connected. The signaling unit is the special modem that converts the DC signaling protocol into tones th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
