电信专业英英词典I-1（在线收听）

　　I-MAC

　　isonchronous media access controller

　　IDN

　　integrated digital network

　　IEC

　　International Electrotechnical Commission

　　Impairments

　　Impairments is the (e.g., transmission channel and signal impairments) degradation caused by practical limitations of channels, (e.g., signal level loss or attenuation, echo, various types of signal distortion, etc.) or interference induced from outside the channel (such as power-line hum or interference from heavy electrical machinery). The measurement of transmission impairments is an important aspect of predicting whether or not telecommunications systems will sustain the business applications they are intended to support. Signal-to-noise ratio, percent distortion, frequency response, and echo are measurements that define impairments most noticeable by users in analog voice systems.

　　Inbound Signaling

　　Inbound signaling uses not only the same channel path as the voice traffic, but the same frequency range (band) used for the voice traffic.

　　Independent Telephone Company (ITC)

　　ITC is a local exchange carrier that is not one of the 22 divested Bell-operating companies. ITCs are not generally subject to the restrictions of the MFJ, although some of the larger ones are bound by separate consent decrees. Southern New England Telephone and Cincinnati Bell are generally considered ITCs from a regulatory point of view.

　　Integrated Services Digital Network (ISDN)

　　ISDN consists of a set of standards being developed by the CCITT and various U.S. standards setting organizations. The CCITT formal recommendations, adopted in October, 1984, first defined ISDN as ". . . a network, in general evolving from a telephony integrated digital network, that provides end-to-end digital connectivity to support a wide range of services, including voice and non-voice, to which users will have access by a limited set of standard multipurpose user- network interfaces." The concept of user access to an existing integrated digital network (IDN) underlies the ISDN.

　　Inter-LATA Services

　　Inter-LATA services are revenues, functions, etc., that relate to telecommunications originating in one LATA and terminating outside that LATA. An interexchange carrier (IXC) is a company which provides telecommunications services between LATAs. (the domain of IXCs).

　　Intermediate Cross Connects

　　In a premises distribution system, intermediate cross connects are cross-connects located telecommunications closets.