Automatic Recognition of Spoken Spelled Names for Obtaining Directory Listings

Since July 1976, an automatic directory assistance system has been available at Bell Laboratories via a dialed-up connection which provides Bell Laboratories telephone directory information in response to TOUCH-TONE® dial inquiries.1,2 The system has been implemented on a Data General Nova 800 laboratory computer and makes use of an ADPCM (adaptive differential pulse-code modulation) voice-response system, 3 which is interfaced to the computer, to provide instructions and the desired directory information to the calling customer. To use the system, the caller dials the appropriate telephone number and then, following a voice-response prompt, spells out on the TOUCHTONE dial the last name and initials of the individual for whom directory information is desired. A caller's spelled inquiry on the TOUCH-TONE dial can be compared directly with the names in a TOUCH-TONE version of the telephone directory and a list of possible matches compiled. In approximately 75 percent of all inquiries for which matches are obtained, matches are unique. For the remaining 25 percent, multiple matches are obtained due to individuals whose 1797