An automatic number announcement circuit (ANAC) is a component of a central office of a telephone company that provides a service to installation and service technicians to determine the telephone number of a telephone line. The facility has a telephone number that may be called to listen to an automatic announcement that includes the caller's telephone number. The ANAC facility is useful primarily during the installation of landline telephones to quickly identify one of multiple wire pairs in a bundle or at a termination point.
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from Greek: τῆλε and φωνή, together meaning distant voice. A common short form of the term is phone, which came into use early in the telephone's history. Nowadays, phones are almost always in the form of smartphones or mobile phones, due to technological convergence.
In telecommunications, a network interface device is a device that serves as the demarcation point between the carrier's local loop and the customer's premises wiring. Outdoor telephone NIDs also provide the subscriber with access to the station wiring and serve as a convenient test point for verification of loop integrity and of the subscriber's inside wiring.
In telecommunication, the term outside plant has the following meanings:
The T-carrier is a member of the series of carrier systems developed by AT&T Bell Laboratories for digital transmission of multiplexed telephone calls.
A varistor is a surge protecting electronic component with an electrical resistance that varies with the applied voltage. It has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. Unlike a diode however, it has the same characteristic for both directions of traversing current. Traditionally, varistors were indeed constructed by connecting two rectifiers, such as the copper-oxide or germanium-oxide rectifier in antiparallel configuration. At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV).
In telephony, the demarcation point is the point at which the public switched telephone network ends and connects with the customer's on-premises wiring. It is the dividing line which determines who is responsible for installation and maintenance of wiring and equipment—customer/subscriber, or telephone company/provider. The demarcation point varies between countries and has changed over time.
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the "holding current". This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound, light, and heat.
In electrical engineering, spikes are fast, short duration electrical transients in voltage, current, or transferred energy in an electrical circuit.
A surge protector (or spike suppressor, surge suppressor, surge diverter, surge protection device or transient voltage surge suppressor is an appliance or device intended to protect electrical devices in alternating current circuits from voltage spikes, which can arise from a variety of causes including lightning strikes in the vicinity and have a very short duration measured in microseconds.
A telephone line or telephone circuit is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or other signaling medium connecting the user's telephone apparatus to the telecommunications network, and usually also implies a single telephone number for billing purposes reserved for that user. Telephone lines are used to deliver landline telephone service and digital subscriber line (DSL) phone cable service to the premises. Telephone overhead lines are connected to the public switched telephone network. The voltage at a subscriber's network interface is typically 48 V between the ring and tip wires, with tip near ground and ring at –48 V.
The invention of the telephone was the culmination of work done by more than one individual, and led to an array of lawsuits relating to the patent claims of several individuals and numerous companies.
This history of the telephone chronicles the development of the electrical telephone, and includes a brief overview of its predecessors. The first telephone patent was granted to Alexander Graham Bell in 1869.
A reed relay is a type of relay that uses an electromagnet to control one or more reed switches. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, narrow glass tube, the contacts are protected from corrosion. The glass envelope may contain multiple reed switches or multiple reed switches can be inserted into a single bobbin and actuate simultaneously. Reed switches have been manufactured since the 1930s.
In electrical engineering, earth potential rise (EPR), also called ground potential rise (GPR), occurs when a large current flows to earth through an earth grid impedance. The potential relative to a distant point on the Earth is highest at the point where current enters the ground, and declines with distance from the source. Ground potential rise is a concern in the design of electrical substations because the high potential may be a hazard to people or equipment.
British telephone sockets were introduced in their current plug and socket form on 19 November 1981 by British Telecom to allow subscribers to connect their own telephones. The connectors are specified in British Standard BS 6312. Electrical characteristics of the telephone interface are specified by individual network operators, e.g. in British Telecom's SIN 351. Electrical characteristics required of British telephones used to be specified in BS 6305.
A telephone exchange, also known as a telephone switch or central office, is a crucial component in the public switched telephone network (PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling telephone calls between subscribers.
The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, New Jersey, and the last were retired in the same city in 1983.
This glossary of electrical and electronics engineering is a list of definitions of terms and concepts related specifically to electrical engineering and electronics engineering. For terms related to engineering in general, see Glossary of engineering.
