The mechanical recognition of ten spoken words (the digits) with near-perfect precision has been demonstrated under laboratory conditions for a single talker after optimum circuit adjustment for his voice. Such word recognition points to the possibility of automatic voice writing and other voice-controlled operations. The device described is based on two principles—the recognition of sustainable patterns of power versus frequency in speech, and the recognition of the durations of such phonetic patterns in words. An alphabet of only ten patterns is proven adequate for limited word recognition, at least in the case of a single talker. The successful performance of the ten-word digit recognizer for voice dialing of telephone numbers was recorded on a motion picture film shown in the oral presentation. Data from the film are discussed in this paper. This paper describes a working model of a phonetic pattern recognizer built at Bell Telephone Laboratories based on a detailed power-frequency spectrum analysis. Tests, to be discussed, indicate that this device, which supersedes an earlier model, leads to almost perfect digit recognition when set for a particular voice. The device also offers outstanding possibilities in speech transmission. The former application will be described in this paper and the latter in a companion paper.