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Off-hook
In telephony, on-hook and off-hook are two states of a communication circuit. On subscriber telephones the states are produced by placing the handset onto or off the hookswitch. Placing the circuit into the off-hook state is also called ''seizing the line''. ''Off-hook'' originally referred to the condition that prevailed when telephones had a separate earpiece (''receiver''), which hung from its switchhook until the user initiated a telephone call by removing it. When off hook the weight of the receiver no longer depresses the spring-loaded switchhook, thereby connecting the instrument to the telephone line. Off-hook The term off-hook has the following meanings: * The condition that exists when a telephone or other user instrument is in use, i.e., during dialing or communicating. * A general description of one of two possible signaling states at an interface between telecommunications systems, such as tone or no tone and ground connection versus battery connection. Note that if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
On-hook
In telephony, on-hook and off-hook are two states of a communication circuit. On subscriber telephones the states are produced by placing the handset onto or off the hookswitch. Placing the circuit into the off-hook state is also called ''seizing the line''. ''Off-hook'' originally referred to the condition that prevailed when telephones had a separate earpiece (''receiver''), which hung from its switchhook until the user initiated a telephone call by removing it. When off hook the weight of the receiver no longer depresses the spring-loaded switchhook, thereby connecting the instrument to the telephone line. Off-hook The term off-hook has the following meanings: * The condition that exists when a telephone or other user instrument is in use, i.e., during dialing or communicating. * A general description of one of two possible signaling states at an interface between telecommunications systems, such as tone or no tone and ground connection versus battery connection. Note that if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Off-hook Tone
The off-hook tone (also off-hook warning, howling tone, or howler tone) is a telephony signal for alerting a user that the telephone has been left off-hook without use for an extended period, effectively disabling the telephone line. North America The off-hook tone in exchanges of the North American Numbering Plan consists of a superposition of tones with the frequencies 1400 Hz, 2060 Hz, 2450 Hz, and 2600 hertz, played at a cadence of on and off. Section 17.2.8 ''Receiver-Off-Hook (ROH) Tone'' The signal is applied to the local loop by the switching system for |
Permanent Signal
Permanent signal (PS) in American telephony terminology, or permanent loop in British usage, is a condition in which a POTS line is off-hook without connection for an extended period of time.Telcordia Technologies, GR-505-CORE Issue 2, December 2005, ''Call Processing'', Section 4.5.2 This is indicated in modern switches by the silent termination after the off-hook tone times out and the telephone exchange computer puts the telephone line on its ''High & Wet list'' or ''Wetlist''. In older switches, however, a Permanent Signal Holding Trunk (PSHT) would play either an off-hook tone (''howler tone'') or a 480/500 Hz high tone (which would subsequently bleed into adjacent lines via crosstalk). Off-hook tone is a tone of increasing intensity that is intended to alert telephone users to the fact that the receiver has been left off the hook without being connected in a call. Permanent signal can also describe the state of a trunk that is seized but has not been dialed upon, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIL-STD-188
MIL-STD-188 is a series of U.S. military standards relating to telecommunications. Purpose Faced with "past technical deficiencies in telecommunications systems and equipment and software…that were traced to basic inadequacies in the application of telecommunication standards and to the lack of a well defined…program for their review, control and implementation", the U.S. Department of Defense looked to develop a series of standards that would alleviate the problem. By 1988, the U.S. Department of Defense (DoD) issued Instruction 4630.8 (reissued in 1992, 2002, 2004) stating its policy that "all forces for joint and combined operations be supported through compatible, interoperable, and integrated Command, Control, Communications, and Intelligence systems. … nd that all suchsystems developed for use by U.S. forces are considered to be for joint use." To achieve this the director of the Defense Information Systems Agency (DISA) is charged with "developing information techn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Signaling
Line signaling is a class of telecommunications signaling protocols. Line signaling is responsible for off-hook, ringing signal, answer, ground start, on-hook unidirectional supervision messaging in each direction from calling party to called party and vice versa. After an off-hook, line signaling initiates register signaling to accomplish the exchange of telephone numbers of called party and in more modern line-signaling protocols, the calling party as well. While register signaling occurs, line signaling remains quiescent unless the calling party goes on-hook or an abnormal cessation of the call occurs, such as due to equipment malfunction or shutdown or due to network outage upstream in that call-attempt's series of spanned trunks. Line signaling can be conveyed in a single DS0 channel of a trunk. In modern PCM telecommunications, line signaling is represented by the ABCD bits in DS0 #16 of an E1 or a selected DS0 within a T1. Line signaling can also be conveyed within ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hook Flash
On analog telephone lines with special services, a flash or register-recall signal is used to control functions on the public telephone exchange, PBX or VoIP ATA. The term "register-recall" in Europe refers to sending a discrete signal to alert the "register" — the logical system controlling a telephone exchange, that it should accept commands from the end user in the middle of a call. The register was normally disconnected from the circuit once a call was setup. In contemporary telephone systems, the functions of the register are carried out by software and computer hardware, but in previous generations of electromechanical exchanges, using technology such crossbar or Reed relay, the register was often a system of analog electronics or even relay logic. The term "Flash" or "Hook Flash" is commonly used in North America, while in Europe a similar signal is referred to as a register-recall or more commonly "Recall" or simply the "R" button. These signals perform similar functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disconnect Supervision
In telecommunication, supervision is the monitoring of a telecommunication circuit for telephony to convey to an operator, user, or a switching system, information about the operational state of the circuit. The typical operational states of trunks and lines are the idle and busy states, seizure, and disconnect. The states are indicated by various electrical signals and electrical conditions depending on the type of circuit, the type of terminating equipment, and the type of intended service. Answer and disconnect supervision are functions of line signaling that convey circuit seizure and disconnect. Answer supervision indicates that a call has been answered. Disconnect supervision provides a signal that the call has been disconnected. For example, the called party may indicate to the telephone exchange that the call is being disconnected by the called party by allowing loop current to flow in the line, or the called party indicates to the exchange that the call is being answered. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clearing (telecommunications)
Clearing, in telecommunications means: * A sequence of events used to disconnect a call and return to the ready state for the next call setup. It is sometimes, particularly in the context of common-channel signaling, called teardown. * Removal of data from an automated information system (AIS), its storage devices, and other peripheral devices with storage capacity, in such a way that the data may not be reconstructed using normal system capabilities (i.e. through the keyboard). ''Note:'' An AIS need not be disconnected from any external network before clearing takes place. Clearing enables a product to be reused within, but not outside of, a secure facility. It does not produce a declassified product by itself, but may be the first step in the declassification process. See also * Disengagement originator * National Information Systems Security Glossary Committee on National Security Systems Instruction No. 4009, National Information Assurance Glossary, published by the Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ringing (telephony)
Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as ''power ringing'', to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing. Specifications In landline telephones, bells or ringtones are rung by impressing a 60 to 105-volt RMS 20-Hertz sine wave across the tip and ring conductors of the subscriber line, in series with the (typically) −48 VDC loop supply. This signal is produced by a ringing generator at the central office. When the switching system directs a call to a particular subscriber line, a relay on the line card connects the ringing generator to the subscriber lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
End Instrument
In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters or leaves a network. Examples of terminal equipment include telephones, fax machines, computer terminals, printers and workstations. An end instrument is a piece of equipment connected to the wires at the end of a telecommunications link. In telephony, this is usually a telephone connected to a local loop. End instruments that relate to data terminal equipment include printers, computers, barcode readers, automated teller machines (ATMs) and the console ports of routers. See also * Communication endpoint * Data terminal equipment * End system * Host (network) * Node (networking) * Terminal equipment In telecommunication, the term terminal equipment has the following meanings: * Communications equipment at either end of a communications link, used to permit the stations involved to accomplish the mission for which the link was estab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical circuit and to be referred to as ''electronic'', rather than ''electrical'', generally at least one active component must be present. The combination of components and wires allows various simple and complex operations to be performed: signals can be amplified, computations can be performed, and data can be moved from one place to another. Circuits can be constructed of discrete components connected by individual pieces of wire, but today it is much more common to create interconnections by photolithographic techniques on a laminated substrate (a printed circuit board or PCB) and solder the components to these interconnections to create a finished circuit. In an integrated circuit or IC, the components and interconnections are formed on t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Impedance
In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage. Impedance extends the concept of resistance to alternating current (AC) circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude. Impedance can be represented as a complex number, with the same units as resistance, for which the SI unit is the ohm (). Its symbol is usually , and it may be represented by writing its magnitude and phase in the polar form . However, Cartesian complex number representation is often more powerful for circuit analysis purposes. The notion of impedance is useful for perf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
