Bell Telephone Laboratories

At&t Bell Laboratories

American Telephone and Telegraph, Co.

Gabor P Torok

Adam B Craft

Andrew B White

Hans George Mattes

John William Wesner, Jr

Leonard Edward O'Boyle

At least one pair of areas on a circuit pack or substrate is allocated for the placement of electromagnetic interference (EMI) absorbing material, e.g., split ferrite cores. All or a portion of the conductor paths for the circuit are routed between pairs of the allocated areas. After the circuit pack is developed and tested, if EMI suppression is required, the EMI-absorbing material extends around the conductors passing between the pairs of allocated areas using holes formed through the allocated pairs of areas. Such holes are formed prior to circuit assembly or, alternatively, are formed only as needed after circuit testing. A clip is used to secure the EMI-absorbing material to the circuit pack. Advantageously, the insertion and securement of the EMI-absorbing material does not require any soldering or special manufacturing tools or fixtures. Accordingly, it can be readily provided in any manufacturing process.

Technique for reducing electromagnetic interference

The disclosed clock adjustment method and apparatus utilizes a periodically transmitted positive or negative predetermined fixed increment clock phase adjustment signal to phase adjust the clocks of the system. The transmitter clock is periodically compared with a common reference clock and a fixed increment clock adjustment signal is transmitted to the receiver which adjusts its clock by applying the fixed increment clock adjustment signal to the common reference clock. The utilization of a predetermined fixed increment clock phase adjustment signal eliminates the need to send the resolution of the clock adjustment and hence reduces the number of data bits required to send clock information over the communication channel.

Clock adjustment method and apparatus for synchronous data communications

A telautograph system allows a user at one location to write on a special surface, such as a chalkboard, and have the image appear at remote screens. Presently, a user wishing to call attention to an entry already written on the board must make a new line or must circle the item to which the remote viewer's attention is to be drawn. This procedure unduly clutters the image and a system has been devised which provides for a cursor (a graphical hand) to appear on the remote screen when the user touches the input surface at a point. The cursor also appears when the user is writing on the surface so as to call attention to the newly formed images. When pressure on the writing surface is released the cursor remains on the remote screen for a finite period and then automatically disappears, leaving the image unencumbered. When information is being removed from the input surface a graphical eraser appears at the remote screen at the site of the removed information.

Remote chalkboard automatic cursor

This disclosure discloses a graphics transmission system using a chalk writing blackboard, a transceiver and a memory. The blackboard is a pressure-sensitive device under control of circuitry in the transceiver producing indicia of the instantaneous position of the chalk on the writing surface. An eraser tray and eraser at its base provide a means to automatically condition the transceiver to interpret a pressure as erase rather than a write command, simply by the absence of the eraser from the tray. Further signal processing yields a more faithful sampling and reproduction of the written signal. A tape recording adjunct is interconnected through a modulation and phase lock loop network that reduces transmission channel and recorder-introduced signal distortion both in the record and the playback modes.

Graphics transmission system

A credit verification terminal for use in several credit systems includes a dual purpose mechanism for sequentially propelling a user's credit card past a reading head, and for storing merchant identifying and other data that can be read by the head. In one embodiment, the mechanism comprises an axially movable drum containing coaxial bands of encoded data. As the drum is rotated, a selected band containing merchant data is read; further drum rotational propels a credit card past the head, so that the user data contained thereon is read. In another embodiment, a planar card carrier includes a movable table containing parallel stripes or rows of encoded merchant and other data on one surface thereof. The user's credit card placed on the carrier is propelled past the head in one direction, and the data recorded is read; with the card removed, the merchant data is read when the carrier is moved past the head to its initial position. Apparatus for changing the stored merchant information is described.

Credit verification terminal with dual information sources

A graphical input terminal includes a pair of resistive sheets separated by an air gap. An energizing voltage is alternately applied to each sheet while an output voltage representative of the position of contact between the sheets caused by the pressure of a stylus, is derived from the nonenergized sheet. A circuit for indicating stylus up/stylus down status without undue interference from capacitively induced voltages is also provided.

Growing community of inventors

Holmdel, NJ, United States of America

Gabor P Torok