Telephonic communications – Call or terminal access alarm or control – At substation
Patent
1987-09-24
1988-12-27
Brown, Thomas W.
Telephonic communications
Call or terminal access alarm or control
At substation
379 36, 379132, 379144, 379145, H04M 127, H04M 166, H04M 1524
Patent
active
047946423
ABSTRACT:
Control equipment employed in a customer-owned public telephone station prevents a user from making unauthorized telephone calls in a telephone system. Operating under the control of a computer in the station, the control equipment employs a call screening process which restricts the telephone numbers a user can dial to those numbers preselected by a station owner. The telephone numbers are categorized in multiple but distinct groups, each of which represents a specific class of telephone call. The control equipment is responsive to momentary loop breaks occurring on tip and ring lines connecting the station to a central office, and to a loop break provided by the central office which reflects that the far end party has disconnected. The control equipment is also responsive to scheduled as well as unscheduled receipt of dial tone. The combination of the call screening process along with the ongoing loop break and dial tone detection and analysis conveniently provides the desired protection so that the user will be properly charged for telephone calls made from the station. The restrictions incorporated in the station for obtaining this protection are applied with minimal inconvenience for the legitimate user.
REFERENCES:
patent: 3985972 (1976-10-01), Rolin et al.
patent: 3996425 (1976-12-01), Low et al.
patent: 4012602 (1977-03-01), Jackson
patent: 4278844 (1981-07-01), Jones
patent: 4314108 (1982-02-01), Sharvit
patent: 4332982 (1982-06-01), Thomas
patent: 4425480 (1984-01-01), Tischin
patent: 4595983 (1986-06-01), Gehalo et al.
Arbabzadah Mohammad A.
Maybach Richard L.
Sanakkayala Bhaskar N.
Verma S. Devendra K.
American Telephone and Telegraph Company AT&T Bell Laboratories
AT&T Information Systems Inc.
Brown Thomas W.
Williamson Samuel R.
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