Method and apparatus for automatically identifying an individual calling

Abstract

After description of a number of prior art automatic telephone number identification systems and certain problems associated therewith, a new method and apparatus for use in such systems which overcomes the problems of the prior art is described. In its preferred form, the method includes the steps of applying to the telephone line at a central office a voltage which has a magnitude sufficient to produce a first predetermined value of loop current in the telephone line. At each party station, the loop current is caused to change between the first predetermined value and a second predetermined value in a manner unique to that party station, with the second predetermined value being smaller than the first predetermined value but greater than a value of loop current that would signify to the central office that an on-hook condition exists on the telephone line. At the central office, the loop current change is detected and compared with a plurality of stored loop current changes to provide party station identification, with each stored loop current change being unique to each party station. In a preferred embodiment, these steps occur in a predetermined time sequence, with the loop current changes also occurring at predetermined but distinct time intervals, each of which is unique to a party station. The apparatus for practicing this method includes an automatic party identifier for location at the central office and a subscriber module adapted to be located in circuit with a party station and the telephone line.