Fraud prevention in a public telephone station

Abstract From the Canadian patent

Abstract, Control equipment employed in a customer-owned public telephone station prevents a user from making unauthorized telephone calls in the telephone system. Operating under the control of a computer in the station 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 ongoing loop break and dial tone detection and analysis conveniently provides the desired protection for reliable …