ITU-T - International Telecommunication Union/ITU Telcommunication Sector
适用范围
This Recommendation applies to the testing of automatic level control (ALC) devices intended for use in digital network-based equipment. An ALC device is defined as any signal processing function located in the digital transmission path which automatically adjusts the level of a signal towards a predetermined value. Devices which modify the frequency response or spectral content of the signal in such a way as to affect the overall level of the signal are also defined as ALC devices for the purpose of this Recommendation. This Recommendation does not apply to subscriber-based level control devices@ devices that operate in the analogue domain@ or any means of fixed level control within the network which may be part of an overall network transmission plan. The scope of this Recommendation is to define certain performance constraints for network ALC devices and@ where appropriate@ to define laboratory tests that may be performed on an ALC device to verify that these constraints are met. An ALC device that satisfies all the constraints and passes all of the tests in this Recommendation should ensure (but will not guarantee) that the pre-existing standard of overall network performance (e.g.@ the transmission of speech@ voiceband data and other voiceband signals@ ISDN@ etc.) is not degraded when the ALC device is installed in the network. This Recommendation also describes the general characteristics of ALC devices and indicates what characteristics are important to provide acceptable performance in the network. Issues relating to the interaction of ALC devices with other network and subscriber equipment are also discussed in this Recommendation. This Recommendation does not define a standard algorithm. This Recommendation does not define planning rules@ deployment aspects@ or target levels for ALC devices. This information may be found in [ITU-T G.136].