Abstract: A preceding system to achieve rates higher than 33.6 kbps in the analog modem to digital modem direction. The preceding system modifies the standard THP algorithm to adapt it for use in PCM modems. The present invention overcomes the above-described difficulties by preceding an upstream signal before transmission. In one aspect of the invention, the present invention provides a precoder for generating a mapped constellation signal from an input signal. In one embodiment, the precoder includes a processor configured to generate the mapped constellation signal from the input signal by mapping input signals in a plurality of distinct ranges onto a basic level. The processor is configured to map the plurality of distinct ranges onto the basic level following different arithmetic rules for at least two of the plurality of distinct ranges.

Abstract: In a data recovery circuit, multiple slicer outputs of incoming data for each data bit, e.g., one or more slicer outputs taken at or near the center of the eye and one or more slicer outputs taken at or near the leading edge and/or trailing edge of the eye, are processed in a manner that reduces the bit-error rate relative to the prior art. The data recovery circuit may be combined with state-of-the-art clock recovery circuits to yield improved clock and data recovery (CDR) circuits.

Abstract: A precoding system to achieve rates higher than 33.6 kbps in the analog modem to digital modem direction. The preceding system modifies the standard THP algorithm to adapt it for use in PCM modems. Instead of an arithmetic modulo operation that is implemented in the transmitter, the invention defines a Discrete Modulo Operation as a function of the constellation of levels chosen. This operation performs the function of limiting the amplitude of the transmitted signal.

Abstract: A decoding system to achieve rates higher than 33.6 kbps in the analog modem to digital modem direction. The decoding system modifies the standard Tomlinson Harashima Precoding algorithm to adapt it for use in PCM modems. Instead of an arithmetic modulo operation that is implemented in the transmitter, the invention defines a Discrete Modulo Operation that performs the function of limiting the amplitude of the transmitted signal.

Abstract: A decoding system to achieve rates higher than 33.6 kbps in the analog modem to digital modem direction. The decoding system modifies the standard Tomlinson Harashima Precoding algorithm to adapt it for use in PCM modems. Instead of an arithmetic modulo operation that is implemented in the transmitter, the invention defines a Discrete Modulo Operation that performs the function of limiting the amplitude of the transmitted signal.

Abstract: In a data recovery circuit, multiple slicer outputs of incoming data for each data bit, e.g., one or more slicer outputs taken at or near the center of the eye and one or more slicer outputs taken at or near the leading edge and/or trailing edge of the eye, are processed in a manner that reduces the bit-error rate relative to the prior art. The data recovery circuit may be combined with state-of-the-art clock recovery circuits to yield improved clock and data recovery (CDR) circuits.

Abstract: A system for, and method of, compensating for codec DC offset and a modem incorporating the system or the method. In one embodiment, the system includes: (1) a DC offset compensator that develops and transmits a DC offset indicator signal corresponding to a DC offset present along a transmission path to a receiving codec and (2) a DC offset encoder, coupled to the DC offset compensator, that receives the DC offset indicator signal and applies a time-varying DC offset compensating signal based thereon to a user data symbol stream transmitted along the transmission path.

Abstract: Techniques are disclosed for providing interoperability between a first modem and a calling identity delivery on call waiting (CIDCW) service. According to an embodiment disclosed herein, a first modem is coupled to an alerting signal receiver and a communications re-establishment device. The alerting signal receiver receives an alerting signal generated in response to an incoming call from a third party line if the first modem is communicating with a second modem. The communications re-establishment device reestablishes communications between the first modem and the second modem after the alerting signal receiver receives an alerting signal. The first modem is equipped to receive the alerting signal and reestablish communications with the second modem independent of the specific capabilities of the second modem, so that these techniques can be utilized in conjunction with a second modem not constructed in accordance with the embodiments disclosed herein.

Abstract: The general problem of conveying a particular meaning in a message so that the meaning is most understandable when an abridged version of the message is displayed is solved by supplying as the message a "tagged" string in which all characters in the unabridged version of the string are tagged with respective priority indicators each having a value indicating a particular priority level. In a station set, an abridged version of the string for a particular priority level is determined by selecting all characters from the received, unabridged version having a priority indicator value equal to or greater than that particular priority level. A priority level is selected such that the corresponding abridged string fits within the available display length.

Abstract: A tagged string is developed by setting the value of a current priority variable to the maximum priority level, selecting a shortest length string of the plurality the characters of which have not all been incorporated into the tagged string as the current string, selecting a character of the current string that is not found in the string that was processed for incorporation into the tagged string immediately prior to the current string, adding the selected character to the tagged string and setting the value of the priority indicator for the just added character to the value of the current priority value. Character selection, addition and priority setting are repeated until the characters of the current string are all incorporated into the tagged string. Thereafter, the value of the current priority variable is decreased. The process, except for the setting of the current priority level, is repeated until all strings have been incorporated into the tagged string.

Abstract: An approach for operating modems in synchronism with the A/D and D/A converters of the network limits the analog signals transmitted to the modem to low levels and concurrently restricts the received signals to large steps. This set of apparently conflicting signal limitations is achieved with a signal conversion process interposed in the communication path between the two hybrids. In one embodiment of this invention, the code conversion is implemented in an adjunct processor that is associated with a switch that participates in the communication path between the two modems. In operation, a call that needs the conversion process is identified by virtue of the calling party's number and service associated service provision information. When it is established that both the calling party's modem and the receiving party's modem operate in the manner that requires signal conversion, conversion is executed.

Abstract: A modem that operates reliably at a symbol rate that corresponds to twice its bandwidth even when it is coupled to a receiving A/D converter that operates under control of a clock is realized by synchronizing the modem's operation to the A/D's clock. The superior operation of this modem advantageously extends to A/D clock frequencies beyond the frequency of twice the modem's bandwidth. To minimize quantization noise, the modem's output is conditioned to minimize intersymbol interference by adjusting the modem's output to the A/D converter's sampling times and slicing levels. When the A/D's clock is higher than twice the bandwidth of the modem's output signal, some intersymbol interference cannot be avoided. In accordance with this invention, the position and value of this interference is computed at the receiver and subtracted from the received signal.

Abstract: A single medium (audio) voice grade call initiated by an ISDN video phone and directed to another ISDN video phone is converted into a multimedia (audio and video) ISDN call by a) maintaining the connection for the voice grade call while the ISDN audio and video connection is being established over a bearer channel of the ISDN subscriber loop different from the bearer channel being used by the voice grade connection, b) switching the audio signals from the voice grade call to the ISDN audio and video connection, once the ISDN audio and video connection is established, and c) tearing down the initial voice grade call.

Abstract: In a video telephony system, a coaxial cable network, which is preferably a part of an existing cable television system, provides a local link for the transmission of the video telephone signals between each originating and destination location and a respective "head end" located on the cable company premises. Each of the head ends is connected to a "point of presence" of a telephone interexchange carrier so that a connection between pairs of head ends, and thus between a pair of video telephone locations, can be made via a switched digital network maintained by the carrier. Certain of originating and destination locations comprise a standard television set, serving as the audio/video display, and a consumer-type camera or camcorder, serving as the audio/video source. Others of the originating and destination locations comprise ISDN video telephones which are connected to the various points of presence of the interexchange carrier via local exchange carrier telephone networks.