In this paper, an on-line prototype of Mandarin speech telephone number inquiry system is implemented on a Windows 95-based PC platform with a telephone interface card supporting TAPI driver and a 16-bit sound card. It is an integration of a speaker-independent, isolated-word Mandarin speech recognition sub-system and a Mandarin text-to-speech (TTS) sub-system. Currently, the vocabulary to be recognized comprises 1922 names of bank and insurance companies with lengths ranging from 2 to 14 syllables. Word recognition rates of 93.6% for top-1 and 98.5% for top-10 were achieved. All output speech messages including the welcome speech and the inquired telephone number are responded by the TTS sub-system.