Bell Telephone Laboratories

Edward Myron Prell

Terrence Thomas Quin

David Cartwright Peterson

Barry William Rogers

Frank Valentine Beck

This invention relates to coin-operated telephones and apparatus for preventing the accidental or fraudulent simulation of coin deposit signals. At the beginning of each coin call or overtime period, a coding algorithm is randomly chosen at the coin station and the identity of the chosen algorithm is transmitted over the telephone line to a receiving telephone office. For each coin deposited, the coin station generates accumulated coin deposit information, codes it in accordance with the chosen algorithm and then transmits the coded accumulated deposit information to the telephone office. The office decodes the received information in accordance with the chosen algorithm identity information previously received at the telephone office to ascertain the amount deposited at the coin station.

Coin telephone antifraud system

A diagnostic system is disclosed for detecting malfunctions in the access circuitry utilized to control the reading, writing, and refreshing of a plurality of semiconductor memory modules. More specifically, a pair of access circuits are provided for each module with each access circuit only controlling the accessing of predetermined bits of each word stored in that module. During read or write operations, the output signals generated by each of the two access circuits for application to the memory elements in that module are 'compared' to ensure that the memory elements are being properly accessed. During refresh operations, the outputs of each pair of access circuits are also 'matched' to ensure the integrity of the refresh operation.

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St. Charles, IL, United States of America

Edward Myron Prell