Call screening in a public telephone station

A method of restricting selected telephone calls originating at a telephone station, the station having a pair of lines for connecting to a switching facility and establishing a telephone connection, the method comprising the step of:

• entering into a plurality of memories data reflective of telephone numbers categorized in distinct groupings, the plurality of memories including;
• a first memory containing data reflective of a group of telephone numbers to which no calls may be made;
• a second memory containing data reflective of a group of telephone numbers to which free calls may be made;
• a third memory containing data reflective of a group of telephone numbers to which charge calls may be made;
• the method further comprising the steps of:
• comparing each digit of a telephone number entered at the station with data reflective of a digit having a positional correspondence repectively within each memory to the entered digit;
• providing a signal in the station in response to a favorable comparison of the entered digit and the data in the first memory for preventing the completion of a telephone call;
• and
• transmitting the entered digit by the station over the pair of lines to the switching facility in response to a favorable comparison of the entered digit and the data in the second and third memory.

A circuit for use in a telephone station for restricting selected telephone calls originating at the station, the station having a pair of lines for connecting to a switching facility and establishing a telephone connection, the circuit comprising:

• a plurality of memory means for containing data reflective of telephone numbers categorized in distinct groupings, the plurality of memory means including:
• a first memory means for containing data reflective of a group of telephone numbers to which no calls may be made;
• a second memory means for containing data reflective of a group of telephone numbers to which calls may be made;
• the circuit further comprising comparison means for comparing each digit of a telephone number entered at the station with data reflective of a digit having a positional correspondence respectively within each memory means to the entered digit, a favorable comparison of the entered digit and the data in the first memory means preventing the completion of a telephone call, a favorable comparison of the entered digit and the data in the second memory means enabling the entered digit to be transmitted by the station over the pair of lines to the switching facility.

A method of restricting selected telephone calls originating at a telephone station, the station having a pair of lines for connecting to a switching facility and establishing a telephone connection, the method comprising the step of:

• entering into a plurality of memories data reflective of telephone numbers categorized in distinct groupings, the plurality of memories including;
• a first memory containing data reflective of a group of telephone numbers to which no calls may be made;
• a second memory containing data reflective of a group of telephone numbers to which calls may be made;
• the method further comprising the steps of:
• comparing each digit of a telephone number entered at the station with data reflective of a digit having a positional correspondence respectively within each memory to the entered digit;
• providing a signal in the station in response to a favorable comparison of the entered digit and the data in the first memory for preventing the completion of a telephone call;
• and
• transmitting the entered digit by the station over the pair of lines to the switching facility in response to a favorable comparison of the entered digit and the data in the second memory.