Staff writerEver been harassed by incessant prank calls? Felt nervous about picking up the phone, not knowing who's on the other end of the line?Based on such apprehensions and other misuses of the telephone, Nippon Telegraph and Telephone Corp. has shrewdly developed a new business. Starting Sunday, the telecommunications giant will offer the Caller ID Display Service, enabling clients to see the caller's number before picking up the phone. To benefit from the new service, applicants must first purchase a special telephone with a display window or a separate adapter. Subscribers will then be charged 400 yen a month for residential use or 1,200 yen for business use, in addition to an initial 2,000 yen to install the system.Callers from general subscriber telephones will have their numbers displayed to anyone with the caller ID service, unless they specifically ask NTT for "per-line blocking," designed to conceal their numbers from anyone they call. NTT also offers another method of maintaining caller privacy. Called "per-call blocking," the service requires callers to dial 184 before placing a call to indicate their wish to have their numbers concealed.These two blocking methods, however, can be overruled by receivers equipped with the Anonymous Call Rejection system. Though the caller ID service has been largely welcomed among business circles and those plagued by unwanted phone calls, it has stirred controversy among experts and the media over the privacy of callers."With an increasing number of stalkers, for example, some people receive prank calls hundreds of times a day," said Akira Ishitobi of NTT's service management department. "We've developed the system as an effective countermeasure against such nuisances at the instruction of the Posts and Telecommunications Ministry."According to a random poll conducted by NTT in 1995, 80 percent of the some 410 general telephone subscribers surveyed had received prank calls at some time. About 62 percent of such nuisances were silent calls, in which the caller does not say anything, 42 percent were wrong numbers, 38 percent were telemarketers and 35 percent were obscene calls, according to the multiple-answer poll."The ID display service provides subscribers with an opportunity to decide whether to accept a phone call," Ishitobi said. "It'll put them on equal terms with callers who previously had the upper hand." And NTT claims that the Caller ID Display Service will also work miracles for businesses.By adopting the service to their Computer Telephone Integration systems, businesses will be able to call up relevant client information from their databases the moment a customer calls, NTT says. Some companies have already taken up the service; NTT began test-marketing it last April in Fukuoka, Nagoya and Yokohama.Daiichi Kotsu Sangyo, based in Kitakyushu, is among the firms using the new service to facilitate business operations. A Fukuoka branch of the taxi and real estate firm has taken advantage of the system for allocating cabs to customers who make reservations by phone."Thanks to the service, the number of phone reservations has been boosted 25 percent, while we have managed to cut the number of telephone operators by nearly half," said Masatoshi Konishi, an operations manager for the Fukuoka district. "It spares us the time of going over such details as our customers' names and numbers as well as the whereabouts of their homes and workplaces.