Automatic prank call rejection system for home country direct based on speech recognition technology

A system that automatically rejects prank calls coming through home country direct from abroad, which is one of the international telephone services, is presented in this paper. Home country direct is a service whereby a user can use international telephone services in his/her native language by directly accessing home country's international station operators. Since this service does not require fees for calling operators, prank calls made by children from abroad pose a problem. Thus, an “automatic prank call rejection system” that determines a legitimate user by instructing him in Japanese to say a specific word, and determining him to be a legitimate user if he repeats this word correctly or determining the call to be a prank call otherwise has been developed. When this system was applied to commercial services, it rejected 94.7% of prank calls. Legitimate users erroneously rejected constituted 0.8%. It has been confirmed that erroneously rejected legitimate users ended up being connected by repeating the word correctly ultimately by hanging up the phone and redialing a number of times. This system has been found to reject about 10,000 prank calls a day when applied to the operations of the KDD International Telephone Center since March 1996. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(4): 44–52, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20070