I.N.: Intelligent Network
The Intelligent Network (I.N. or IN) is a network architecture for both fixed and mobile telecommunication networks. It allows operators to to differentiate themselves by providing value-added services in addition to the standard telecoms services such as GSM services on mobile phones. It can also be regarded as an overlay on the core network.

IAC: Initial Alignment Control
Initial Alignment Control (IAC) is an SS7 MTP 2 function that provides the link alignment processing.

IAD: Integrated Access Device
An Integrated Access Device (IAD) is an access device that can simultaneously deliver traditional PSTN voice services, packet voice services, and data services (via LAN ports) over a single WAN link. It aggregates multiple channels of information including voice and data across a single shared access link to a carrier or service provider PoP (Point of Presence). The access link may be a T1 line, a DSL connection, a cable (CATV) network, a broadband wireless link, or a metro-Ethernet connection.

IAM: Initial Address Message
Initial Address Message (IAM) is defined in SS7 (Signaling System No. 7). It is part of the ISUP (Integrated Services Digital Network User Part) call setup. The message is used to seize a circuit and transfer addressing and call handling or routing information. The IAM includes the address and other information relating to routing and handling a call.

ICPIF: Calculated Planning Impairment Factor loss/delay busyout threshold
Calculated Planning Impairment Factor loss/delay busyout threshold (ICPIF) is an ITU-T G.113 standard for measuring quality of service. ICPIF replaces the old QDU (Quantisation Distortion Units) which were a subjective measurement. ICPIF represents predefined combinations of loss and delay in a VOIP network call. Packet loss and delay determine the threshold for initiating the busyout state. Gateways generate ICPIF values for each VoIP call, and these calculations can be stored for each VoIP call record.

IDN: Integrated Digital Network
Integrated Digital Network (IDN) refers to a network that uses both digital transmission and digital switching.

IEC: International Electro-technical Commission
International Electro-technical Commission (IEC) is the authoritative worldwide body responsible for developing consensus global standards in the electrotechnical field. IEC is dedicated to the harmonization and voluntary adoption of these standards, supporting the transfer of electrotechnology, assisting certification and promoting international trade. Since 1906, IEC has served the world's electrical industry, developing international standards to promote quality, safety, performance, reproducibility, and environmental compatibility of materials, products, and systems. It has also published standards for the electronics and telecommunications industries. The IEC's present membership of 51 countries includes most major trading nations.

ILEC: Incumbent Local Exchange Carrier
Incumbent Local Exchange Carrier (ILEC) is a telephone company that was providing local service when the Telecommunications Act of 1996 was enacted. Compare with CLEC, a company that competes with the already-established local telephone business. In most part of the world, ILECs are the Post, Telephone, and Telegraphs (PTTs), government-managed monopolies.

Immediate Start
Immediate Start is a method of E&M (ear & mouth) signaling. When the signaling leads indicate a change to an off-hook state, the interface is immediately ready to send signaling information.

Immediate Start Signaling
Immediate Start Signaling is the most basic of Start Dial Supervision. The originating side goes off-hook, waits for a finite period of time (200ms, for example), then sends the dial digits without regard to the far end. The Immediate Start Signaling method is less reliable than Wink Start. In Immediate Start, there is no wink from the end that receives the call to signify that that is ready to accept digits.

IMT: Inter-Machine Trunk
Inter-Machine Trunk (IMT) is a connecting circuit between two automatic switching centers, both owned by the same company. For example, the trunk between two 4ESS machines of the same ILEC is an IMT.

INB: Install Busy
Install Busy (INB) is a status of operation in many systems. For example, INB may indicate a maintenance operation of the signaling channel during which, apart from this channel not being available for signaling, the configuration parameters (mostly ds0 characteristics of this interface) can be changed. The implementor may chose to just use the busy state as a superset state instead of inB in which case this state will be rendered redundant.

In-Band Signaling
Inband (In-Band) Signalling, also known as robbed-bit signalling, is a type of signalling in which metadata and control information is sent in the same channel used for data. For example, a line uses 8 kbps of each 64 kbps channel for WAN synchronization and signalling. The remaining 56 kbps handle the transmission of user data. T1 access lines containing one or more switched channels, and Switched-56 lines use inband signalling.

Indication of Camp-On
Indication of Camp-On is an audible tone generated by the telephone system. Attendant camp-on service allows an electronic switching system Centrex attendant to hold incoming calls to busy lines. Each time the attendant releases his/her talking connection from the loop involved in the camped-on call, the indication of camp-on tone is heard by the called customer if the customer has subscribed to the indication of camp-on option. The customer may get this tone several times as the attendant reconnects and releases from the loop in response to timed reminders from the console. Indication of Camp On tone is at 440 Hz and -13 dBm0/frequency for one second every time the attendant releases from the loop.

INE: Intelligent Network Element
Intelligent Network Element (INE) is a network element that can be provisioned from a remote Operation Support System (OSS).

INE: Intermediate Network Element
Intermediate Network Element (INE) refers to a line-unit-line termination (LULT) or a line-unit-network termination (LUNT)

INI: Inter-Network Interface
Inter-Network Interface (INI) refers to the point of demarcation in the network where two sub-networks meet when service is provided across multiple sub-networks.

In-Slot Signaling
In-slot Signaling is a signaling information periodically sent (in a digital time slot) that is permanently allocated in the (voice or data) channel time slot.

Intensity Modulation
Intensity modulation refers to the form of modulation in optical communications in which the optical power output of a source is varied in accordance with some characteristics of the modulating signal.

Interactive Media
Interactive media refers to a newly designed telecommunications systems that permit two-way communications between televisions or computers in one location with software stored on a central computer. It's also possible to allow individuals in distant location to communicate, teach, or learn from one another.

Intercepting Loopback Tone
Intercepting Loopback Tone is a steady High Tone sent from an intercept operator to the 'A' board operator in manual offices indicates that an intercept operator has completed the call and that the 'A' should disconnect from the circuit. The completion of intercepted calls in this manner is no longer recommended.

Interchange Circuit
Interchange circuit refers to the circuit that facilitates the exchange of data and signaling information between DTE (data terminal equipment) and DCE (Data circuit-terminating equipment).

Intercom
Intercom, short for intercommunicating telephone, refers to an in-building electronic communications system. This communication system links different rooms within a building or ship etc.

Inter-Exchange Trunk
Inter-exchange trunk is the trunk between IECs which typically contains a 4ESS toll switch.

Interface Standard
Interface standard refers to a standard in telecommunications that defines one or more functional and/or physical characteristics necessary to allow the exchange of information between two or more systems or equipments. An interface standard may include operational specifications and acceptable levels of performance.

Inter-LATA Services
Inter-LATA Services refers to revenues, functions, etc. that relate to telecommunications originating in one LATA and terminating outside that LATA.

Intermediate Cross Connects
Intermediate Cross Connects refers to cross-connects located telecommunications closets within a premises distribution system.

Interoffice Call
Interoffice Call is the telephone call that involves only one switching system. The two parties connected to the same local central office is an example.

Interoffice Channel
Interoffice Channel refers to: (1) In LEC (Local Exchange Carrier) tariffs, the channel connecting two serving wire centers located in two serving COs (Central Office). (2) In IXC (Interexchange Carrier) tariff, the channel connecting two serving IXC POPs (Point of Presence), interoffice transmission facilities used to connect LEC switching systems.

Intersymbol Interference
Intersymbol interference refers to following definitions: (1) Destortion of the received sIntersymbol interference refers to following definitions: (1) Destortion of the received signal in a digital transmission system which distortion is manifested in the temporal spreading and consequent overlap of individual pulses to the degree that the receiver can not reliably distinguish between changes of state (i.e. between individual signal elements). (2) Extraneous energy from the signal in one or more keying intervals that interferes with the reception of the signal in another keying interval. (3) The disturbance caused by extraneous energy from the signal in one or more keying interval that interferes with the reception of the signal in another keying interval.

IntraLATA
IntraLATA refers to a telephone call or circuit which does not cross a LATA boundary. IntraLATA communications require the use of an LEC, but not an IXC (intereXchange Carrier). IntraLATA telephone calls can still be long distance calls. In fact, because intraLATA long distance in the US is not subject to the same competitive market forces as interLATA long distance, intraLATA long distance calls normally cost much more than interLATA long distance.

Intra-Office Trunk
Intra-Office Trunk is the trunk between two pieces of equipments within the same telephone central office.

Intrastate
Intrastate, in telecommunication, refers to a call that remains entirely within the boundaries of a single state so that it falls under the jurisdiction of that state's telephone regulatory procedures.

Inverse Multiplexing
Inverse multiplexing is one of the multiplexing scheme in telecommunications. Not like the ordinary multiplexing which combines multiple signals into a single signal, inverse multiplexing speeds up data transmission by dividing a data stream into multiple concurrent streams that are transmitted at the same time across separate channels (like a T1 or E1 lines) and are then reconstructed at the other end back into the original data stream.

Inward Trunk
Inward Trunk is a trunk that is only for incoming calls. In another words, these trunks cannot be used for dialing out. An example of this is 800 lines.

IN-WATS: Inward Wide Area Telephone Service
Inward Wide Area Telephone Service (IN-WATS), similar to the 800 services, refers to service of interexchange carriers, such as formal AT&T, Sprint, local exchange carriers, independent phone companies, and long distance resellers in North America which allows subscribers to receive calls from specified areas and being charged for the call and with no charge to the calling party.

IOC: Independent Operating Company
Independent Operating Company (IOC) refers to the independently-owned company providing local telephone services to residential and business customers in a geographic area not served by a Reginal Bell Operating Company (RBOC).

IP Centrex
IP Centrex is the Central Office Exchange Services (Centrex) for enterprises based on the IP telephony technologies. The traditional Centrex is a telephone switch service used by enterprises in which switching occurs at a central (local) office. In IP telephony, voice conversations can be digitized and packetized for transmission across the network. IP Centrex refers to a number of IP telephony solutions where Centrex service is offered to a customer who transmits its voice calls to the network as packetized streams across a broadband access facility.

IP-PBX
The IP-PBX is a telephone switch based on the VoIP technologies which is used by enterprises and located at the premises of a company and offers easier user administration and advanced applications. With an IP-PBX, the Local Area Network is the platform for connecting IP phones over a packet network to the call manager. This unifies the data applications and the voice network, but places demands on the packet prioritization aspects of the LAN infrastructure to ensure user satisfaction with the quality of audio.

ISC: International Switching Carrier
International Switching Carrier (ISC) is an exchange which has the function of switching telecommunications traffic between the national network and the networks of other countries.

ISDN BRI
An ISDN Basic Rate Interface (ISDN BRI) is a type of ISDN interfaces that uses two B channels for user data, and one 16-kbps D channel for ISDN D-channel signalling. Both B channels can be switched; both channels can be nailed up; or one channel can be switched and the other nailed up. A line of this type can connect to standard voice service, Switched-56 data service, or Switched-64 data service.

ISDN D-Channel Signalling
ISDN D-channel Signalling is a type of out-of-band signalling in which a D channel handles WAN synchronization and signalling, and the B channels carry the user data. T1 PRI, E1 PRI, and ISDN BRI lines use ISDN D-channel signalling.

ISDN H-Channel
ISDN H-Channel is a special, high-speed clear channel. H channels, designed primarily for full-motion color video, are not yet in common use. There are currently three kinds of H channel: H0 ("H-zero"), H11 ("H-one-one"), and H12 ("H-one-two"). An H0 channel operates at 384 Kbps (roughly one fourth of the North American Primary Rate Access or one fifth of a European Primary Rate Access). An H1 channel operates at 1.536 Mbps and occupies the whole North American Primary Rate Access. An H12 channel occupies the entire European Primary Rate Access.

ISDN PRI: ISDN Primary Rate Interface
ISDN Primary Rate Interface (ISDN PRI) is the ISDN configuration used primarily by large organizations with intensive communications needs. An ISDN PRI connection supports 23 64 kbps B-channels and one 64 kbps D-channel (or 23B+D) over a high speed DS1 (or T-1) circuit. The European PRI configuration is slightly different, supporting 30B+D.

ISDN: Integrated Services Digital Network
Integrated Services Digital Network (ISDN) is a system with digitized phone connections. For decades, telephony has used purely analogue connections. This is the first protocol to define a digital communications line that allows for the transmission of voice, data, video and graphics, at high speeds, over standard communication lines. The various media are simultaneously carried by bearer channels (B channels) occupying a bandwidth of 64 kbits per second (some switches limit bandwidth to 56 kb/s). A defined data channel (D channel) handles signaling at 16 kb/s or 64 kb/s, depending on the service type.

Isochronous Signal
Isochronous Signal is periodic signals in which the time interval that separates any two corresponding significant occurrences or level transitions is always equal to some unit interval or a multiple of that unit interval. For example, in digitized voice signals, ideally voice samples occur isochronously at precisely the sampling interval or frame rate. Packet data signals are not isochronous.

ISUA: SS7 ISUP-User Adaptation Layer
SS7 ISUP-User Adaptation Layer (ISUA), an integral part of the OpenSS7 SIGTRAN stack, is an SS7 Signalling User Adaptation Layer for providing ISUP-User signalling over SCTP. ISUA is intended to be used on a Provider/User basis where ISUP resides on a Signalling Gateway (SG) and ISUP call control applications reside on an Application Server (AS).

ISUP: ISDN User Part
The ISDN User Part (ISUP), a key protocol in the SS7/C7 signaling system, defines the protocol and procedures used to set-up, manage and release trunk circuits that carry voice and data calls over the public switched telephone network (PSTN) between different switches. ISUP is used for both ISDN and non-ISDN calls.

ITC: Independent Telephone Company
Independent Telephone Company (ITC) is a local exchange carrier that is not one of the divested Bell-operating companies (there were 22 such companies before). ITCs are not generally subject to the restrictions of the MFJ (Modification of Final Judgment), although some of the large ones are bound by separate consent decrees. Southern New England Telephone and Cincinnati Bell are generally considered ITCs from a regulatory point of view.

ITSP: Internet Telephone Service Provider
Internet Telephone Service Provider(ITSP) refers to the company who provides "voice Over IP" services.

ITU: International Telecommunication Union
International Telecommunication Union (ITU) is an organization established by the United Nations to set international telecommunications standards and to allocate frequencies for specific uses.

ITU-T: International Telecommunication Union Telecommunication Standardization Sector
International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is an international body under the International Telecommunication Union (ITU) that develops worldwide standards for telecommunications technologies. The ITU-T carries out the functions of the former CCITT.

IUA: ISDN Q.921-User Adaptation Layer
ISDN Q.921-User Adaptation Layer(IUA), a protocol in the SIGTRAN protocol suite, defines a method for backhauling of ISDN Q.921 User messages over IP using the Stream Control Transmission Protocol (SCTP). IUA is used between a Signaling Gateway (SG) and Media Gateway Controller (MGC). It is assumed that the SG receives ISDN signaling over a standard ISDN interface.

IVR: Interactive Voice Response
Interactive Voice Response (IVR) is a feature in a telephone system that provides information in the form of recorded messages over telephone lines in response to user input in the form of spoken words or, more commonly, DTMF signaling. Examples include banks that allow customer to check their balance from any telephone, and an automated stock quote system.

IXC: Inter-Exchange Carrier
Inter-Exchange Carrier (IXC) is a long-distance telephone company. The task of an IXC is to connect Local Exchange Carrier (LECs) and allow customers to place interLATA telephone calls.