IEEE 269-1992 pdf download.IEEE Standard Methods for Measuring Transmission Performance of Analog and Digital Telephone Sets.
Abstract:Practical methods for measuring the transmission characteristics of both digital and conventional to wire analog telephone sets by means of objective measurements on a test connection are described. The test results thus obtained may be used as a means of evaluating or specifying the transmission performance of a telephone set on a standardized basis. The measurements are applicable to telephone sets incorporating carbon or linear transmitters. Measurements are over the frequency range most useful for speech: 100-5000 Hz. The test methods are not intended to be applicable to special devices, such as noise-exclusion transmitters, distant-talking transmitters, insert-type receivers, or noise-exclusion receivers equipped with large ear pads.
Keywords: analog telephone sets, digital telephone sets, telephony, voice transmission performance.
The purpose of this standard is to describe practical methods for measuring the transmis- sion characteristics of a telephone set by means of objective measurements using a test connection. Although the various methods generally produce similar results, some deviations can be expected depending on telephone characteristics Measurement conditions should be noted when reporting results. The test results thus obtained may be used as a means of evaluating or specifying the transmission performance of a telephone set on a standardized basis.
IEEE 269-1992 is intended for measuring the transmission performance of conventional two wire analog telephone sets and digital telephone sets. These telephone sets can be equipped with handsets or headsets using carbon or linear transmitters. This standard covers measure ments over the frequency range most useful for speech, 100 Hz to 5000 Hz. This standard is not intended to be applicable to special devices such as noise exclusion transmitters, loud speaking telephones, or noise exclusion receivers equipped with large ear pads. Drawings and test procedures, as well as other pertinent information, are included as an aid in setting up the tests.
The approach taken in this standard to measure digital telephone sets is to convert the dig- ital signal to or from the telephone set via an interface and a reference codec to an analog sig- nal, and then to use standard analog measurement techniques. Although not covered in this standard, direct signal processing in the digital domain could be used.
Where an input signal, electric or acoustic, is required for making the objective measure ments, either of two specified signals may be used, i.e., sinusoidal or continuous spectrum The two types of signal will give essentially identical results for telephone sets measured in the linear region of their operation, when the measurement is sufficiently noise free. For tele- phone sets incorporating nonlinear devices, however, the continuous spectrum signal is pref- erable. Nonlinear devices include carbon microphones, compressors, automatic gain control (AGC)circuits, etc.IEEE 269-1992 pdf download.