Abstract: In a simultaneous voice and data communications system, a voice signal is added to a data signal before transmission over the public switched telephone network (PSTN). In particular, in every signaling interval, a signal point is selected for transmission as a function of both the voice signal and the data signal. Since the voice signal is effectively offset by the data signal, compandors normally found in the PSTN are not effective in improving the signal to noise ratio of the transmitted voice and data signal. Therefore, the voice signal is additionally companded in the transmitter before transmission over the PSTN. This additional companding by the transmitter improves the signal to noise ratio of the combined voice and data signal.

Abstract: A simultaneous voice and data (SVD) communications system includes an SVD modem at either endpoint of the system. Each SVD modem provides an SVD signal to the opposite endpoint, where this SVD signal includes both a voice channel and a data channel. One, or both, of these SVD modems allows the respective user to alter either the voice signal that is provided to that user, or the voice signal that is transmitted from that user, via the voice channel of the SVD signal, to the opposite SVD endpoint.

Abstract: A passive optical network architecture is disclosed for application in a local loop telephone environment. A local digital switch transmits an optical signal bearing information downstream over an optical fiber to the terminal equipment of a group of subscribers. This transmitted optical signal comprises light at a number of different wavelengths, i.e., it is a wavelength-division multiplexed signal, where each subscriber is associated with a particular wavelength of light. Each subscriber's terminal equipment detects that portion of the transmitted optical signal that exists at its assigned wavelength and thereby recovers the information sent by the local digital switch for that subscriber. However, a fraction of this detected optical signal is then remodulated by the subscriber's equipment with the subscriber's upstream information and returned to the local digital switch. As a result, no optical sources exist in the subscriber equipment in this optical network architecture.

Abstract: A low-voltage drop current regulator regulates the current in a data interchange circuit. In one embodiment, the low-voltage drop current regulator couples a positive power supply voltage to the power supply pin of a driver integrated circuit. In another form of the invention, the low-voltage drop current regulator is placed in series with the individual output leads of a driver integrated circuit to couple the respective output signals to respective pins of the data interchange circuit.

Abstract: In a wave solder manufacturing process, a test device is used to measure the contact-area between a solder wave and a printed wiring board. In particular, the test device is a printed wiring board (PWB) that includes at least two arrays of electrical contacts, one array near each side of the PWB. As the PWB makes contact with a solder wave, the number of electrical contacts in each array that are grounded by the solder wave are counted and displayed on an alpha-numeric display mounted on top of the PWB. This "distance-based" measurement provides an accurate determination of the uniformity of the contact-area, and concomitantly the dwell-time of the soldering process. This test device provides a basis for real-time adjustment of solder wave height, and end-to-end balance, in a solder wave machine. In particular a wave solder machine includes a means for receiving contact-area information from the test device and a means for adjusting the solder wave in response to the contact-area information.

Abstract: A "Personal Computer Memory Card International Association" (PCMCIA) peripheral, e.g., a modem, incorporates a shared memory interface to a personal computer. This shared memory interface provides the capability to easily program the PCMCIA peripheral either in the factory or in the field. In addition, the shared memory interface removes the requirement of having a resident "boot-up" code in the PCMCIA peripheral. Finally, the shared memory interface provides the capability to transfer user data from the personal computer, i.e., data terminal, to the PCMCIA modem at a higher data transfer rate than is currently available via the modem's universal asynchronous receive/transmit (UART) integrated circuit.

Abstract: In a wave solder manufacturing process, a test device is used to measure the contact-area between a solder wave and a printed wiring board. In particular, the test device is a printed wiring board (PWB) that includes at least two arrays of electrical contacts, one array near each side of the PWB. As the PWB makes contact with a solder wave, the number of electrical contacts in each array that are grounded by the solder wave are counted and displayed on an alpha-numeric display mounted on top of the PWB. This "distance-based" measurement provides an accurate determination of the uniformity of the contact-area, and concomitantly the dwell-time of the soldering process.

Abstract: A self-synchronizing scrambler/descrambler arrangement operates in two modes. In the first, or start-up mode, predetermined data is coupled to the scrambler and transmitted to the descrambler. This data is used to "seed", i.e., load, storage devices in the scrambler and descrambler with the same information. After a predetermined time interval, the start-up mode is terminated, and the scrambler and descrambler each operate in a steady-state mode. In this mode, the information loaded in the scrambler and descrambler devices are used to form the scrambler and descrambler key signals. Advantageously, in the steady-state mode, the occurrence of transmission errors does not effect the contents of the storage devices in the scrambler and descrambler. Hence, the prior art problem of error multiplication is avoided.

Abstract: A communications system simultaneously transmits both a primary data signal and a secondary voice signal in such a way that the dynamic range of the secondary voice signal is increased even though deliberate errors are introduced into the transmitted data portion of the signal. In particular, the communications system includes an error correcting technique like channel encoding and the constellation signal space is divided into a number of regions, where at least one of the regions overlaps with another region. The primary signal is channel encoded to select a particular one of the number of regions, the region being represented by a reference signal point value. The voice signal is encoded to provide a signal point vector, which is added to the reference signal point in such a way that the resultant signal point is located in the overlapping region thereby deliberately introducing an error into the resulting transmitted signal point stream.

Abstract: A simultaneous voice and data (SVD) modem is coupled to both a fax machine, which includes a fax modem, and a telephone set. When the fax machine initiates a fax-call, the SVD modem emulates signaling of the local loop. This allows the fax machine to operate without requiring modifications to the fax machine. After establishing a data connection with a far-end SVD modem, the near-end SVD modem demodulates the fax modulation signal from the fax machine to recover the fax data. The fax data is then re-modulated using a data modulation technique for transmission to the far-end SVD modem. The latter, demodulates the data portion of the signal to recover the fax data, which is then re-modulated using a fax modulation technique for transmission to a far-end fax machine.

Abstract: A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). The hybrid DFE structure is designed so that one form of tap values dominates over the other. This allows only the dominate tap values to be used by the transmitter during precoding and reduces the transmitter complexity. In particular, a hybrid DFE is designed so that the I(z) coefficient values dominate over the N(z) coefficient values, where the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively. A respective Tomlinson precoding scheme in the transmitter uses only the I(z) values. Since only the I(z) values are used in the precoder of the transmitter, the NP-DFE of the receiver is kept active during the communications phase.

Abstract: In transmitting information over a cellular communications channel to an opposite endpoint, a modem's autorating routine is "data-driven." In particular, when the amount of information to transmit to the opposite endpoint is low, the modem's data rate is low e.g., 4800 bps, and the modem's ability to autorate upwards, i.e., fallforward, is disabled. However, when the amount of information to transmit to the opposite endpoint is high the modem's ability to fallforward is enabled so that the modem's data rate can increase to the highest permissible data rate for the cellular channel in order to transmit large blocks of information.

Abstract: In a simultaneous voice and data communication system, a stream of signal points is partitioned into a plurality of symbol blocks, each symbol block including a data segment and a control segment. The data segment carries information from a user, i.e., user data, while the control segment provides control information. A voice signal is then added to at least a portion, or all, of the signal points of each symbol block to provide for simultaneous voice and data transmission to an opposite endpoint. The control information may represent information from a secondary data source, and/or may include information about the characteristics of the succeeding block, e.g., the user data rate, and information pertaining to characteristics of the communications channel.

Abstract: Intersymbol interference and precoding loss are minimized by combining the precoding and coding operations. An intersymbol interference coder uses a feedback loop to apply a dither sequence to a sequence of input signal points. The dither signal applied to each input signal point is a function of the previous signal points in the sequence. The intersymbol interference coder implements, for example, a trellis coding operation by selecting one of several different modulo operations to determine the magnitude of the dither signal, the selection being made in response to the current trellis state. The sequence of signal points output from the intersymbol interference coder generates a valid sequence of the trellis code input to the Viterbi decoder.

Abstract: A mobile phone includes a modem, hereinafter referred to as a cellular radio modem. This cellular radio modem supports two modes of operation--an analog mode, where the cellular radio modem provides an analog signal for transmission; and a digital mode, where the cellular radio modem provides a digital bit stream for transmission. During operation, i.e., the existence of a data connection to a far-end modem, the cellular radio modem is alerted by the cellular network to switch to the appropriate mode--analog or digital. The cellular radio modem then switches and continues transmission in the new mode. In this embodiment, the far-end modem is part of a modem-pool located within the Mobile Telecommunications Switching Office of the cellular network. The far-end modem automatically detects this switch by the cellular radio modem and itself switches to the appropriate mode.

Abstract: Some data communications networks employ the use of both a leased line and a dial-up line between two modems. Typically, the dial-up line provides a backup capability when the leased line causes a degradation in the signal quality of the data signal. This degradation of the signal quality of the data signal is detected by one of the two modems, which then automatically establishes a data connection over the dial-up line. However, it is preferable to switch back to the leased line as soon as possible since the leased line usually costs less than the dial-up line. Therefore, in order to test the leased line, the entire data signal is simultaneously transmitted on both the dial-up line and the leased line. The use of the existing data signal to test the leased line's effect on signal quality allows the modem to perform a more complete analysis of the returned data signal so that a premature transition back to the leased line does not occur.

Abstract: A simultaneous voice and data modem performs "voice-activated" data rate changes to improve the transmission quality of the voice signal. In particular, when the simultaneous voice and data modem detects that a local telephone set has gone "off-hook," the simultaneous voice and data modem selects a signal space with a lower symbol density, which, although resulting in fewer bits per symbol, provides for a higher quality voice transmission.

Abstract: In a simultaneous voice and data communications system, a voice signal is mapped into an N-dimensional signal space constellation as a vector, and added to a reference signal point, i.e., a data symbol, where the data symbol is selected from a constellation of data symbols every signaling interval as a function of a data signal. The constellation signal space is further divided into a number of shaped regions, where each region is associated with a different one of the data symbols. The shape of each region is selected as a function of the characteristics of the voice, or audio, signal. In particular, each region illustratively has a rectangular shape.

Abstract: A monolithic array of surface emitting lasers is used in a printer engine to illuminate a photosensitive surface.

Abstract: In a mobile data communications system, a near-end modem initiates a data connection to a far-end modem at the highest permissible data rate, e.g., at 9600 bits per second (bps). If the communications channel subsequently degrades, either the near-end modem, or the far-end modem, initiates an autorate, or fallback sequence, e.g., to 4800 bps. However, if channel performance is still poor at 4800 bps, then one, or both, of the modems initiate a fallback to 1200 bps--skipping over the data rate of 2400 bps, which is not included within the fallback sequence.