The purpose of this Standard is to describe a practical and reproducible method for measuring the transmission characteristics of a telephone set, and the components thereof, by means of objective measurements in a test connection. Performance characteristics obtained using this method will approximate but will not duplicate performance under actual use conditions. The method requires a suitable Artificial Mouth. It also specifies a standard Artificial Ear, standard circuits comprising direct-current power feed and connecting loops, and a standard pressure microphone. This Standard is intended for use in measuring the transmission characteristic over the frequency range most useful for speech, e.g. 150 to 5000 hertz. It is to be used for single-frequency measurements and for measurements with continuously varying frequencies such as slow sweeps and warble bands. It is suitable also for measuring the transmission performance of conventional telephone sets equipped with handsets using carbon transmitters and used with 2-wire circuits. It is 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. This Standard is based on a standard pressure microphone to measure the sound field produced by the Artificial Mouth and to measure the pressure developed in the Artificial Ear. Drawings and test |