covert%covert.DEC@decwrl.dec.com (John R. Covert) (09/01/88)
In V8#136, Don Ritchey (312) 979-6179, AT&T Bell Laboratories, IH 2F-416 writes: >Almost universally, number screening and the like is handled by a LD >carrier in the nearest switching office. (I see no reason that an AOS >need be any different.) The phone itself would very likely have >absolutely nothing whatsoever to do with blocking access to 10XXX >numbers. (Most phones aren't that smart.) COCOTs are very different than normal payphones. Almost universally, COCOT payphones are microprocessor controlled, and the AT&T manufactured COCOTs are no exception. When the receiver is lifted, dial tone is provided by the phone itself. Digits are interpreted according to tables contained in the telephone, which contain entries detailing not only what digit sequences are allowed, but also which particular carrier to use for each call. The tables are completely under control of the owner of the phone, who can choose to allow or block access to any digit sequence. AT&T would probably get in serious legal trouble if they sold phones which could *not* block access to AT&T! In many cases, the phone doesn't even initiate dialing until *after* the billing information has been entered. A COCOT located in the Acton Center store accepts the billing information and is polite enough to use AT&T if an AT&T card is entered after the number, but contacts an AOS if "0" or nothing is dialed when the caller is prompted by the "bong" for billing information. /john