Abstract: The present invention provides a tap off unit for use in a multiple dwelling unit. The tap off unit includes a housing having an input terminal and an output terminal for interposing the tap off unit in a cable signal line, a plurality of taps disposed within the housing, with each tap having a faceplate including associated signal coupling circuitry, and a circuitry board disposed within the housing. The circuitry board distributes a signal from the cable signal line to each of the plurality of taps within the housing and the plurality of taps are connected in parallel such that one of the plurality of taps may be removed without disruption of the signal to the remaining taps.

Abstract: A regulated power supply for application in a cable signal distribution amplifier comprises a filter, voltage doubler and current sense transformer controlled by a control technique known in the art. In the event of a high impedance short condition causing severe overcurrents, the known control technique is ineffective. To alleviate the problem, a high impedance current fault control circuit includes a sampling circuit, a level adjusting circuit, a differential amplifier for providing a monitor output control voltage and a buffer circuit to the controller. In the event of a high impedance current fault, the control circuit kicks in and interrupts controller operation saving power supply components from damage caused by the overcurrent condition.

Abstract: The present invention provides a method and apparatus for providing program clock reference (PCR) data to various devices in a digital transmission system in a robust manner. According to the present invention, PCR data representative of a snapshot of the system clock is encoded only an existing frequency reference signal. The frequency reference signal is a signal to which all clock dependent components lock to ensure that the proper frequency lock is used. By encoding the frequency reference with PCR data, effectively using the frequency reference as a PCR carrier wave, the PCR is efficiently and robustly delivered to the various devices requiring this PCR data.

Abstract: A system located in a region to determine information about an unknown car relative to a moving train includes first and second satellite navigation receivers, first and second transceivers and first and second controllers. The moving train includes a first car, and the region includes the moving train and the unknown car. The region is defined by points at which radio communication with the first car is possible. The first satellite navigation receiver, located in the first car, provides first location data, and the second satellite navigation receiver, located in the unknown car, provides second location data. The first transceiver is located in the first car, and the second transceiver is located in the unknown car. The first controller, located in the first car, reads the first location data from the first satellite receiver at a first time and sends via the first transceiver a first request to the second transceiver at the first time.

Abstract: A multi-output distribution amplifier includes a forward amplifier and a reverse amplifier and multiple outputs. The forward and reverse paths are separated utilizing low and high pass filters. The geometric mean frequency between the respective pass bands of the high and low pass filters is known as the crossover frequency. A circuit for providing a 180 degree phase reversal such as a balun transformer is connected in series with one (in a dual output arrangement) or half the reverse paths of an arrangement involving three or more forward or reverse paths to improve crossover isolation. For example, in a typical dual output distribution arrangement where the amplifiers are not padded, close to 20 dB of crossover isolation improvement is accomplished by simply connecting a balun transformer in series with one or the other of the low pass filters connected to one or the other forward direction output. At a minimum, a 6 dB improvement can be achieved.

Abstract: A modular meter based utility gateway enclosure which resides between a power meter and a meter socket of a residence or other building supports multiple interchangeable local area network (LAN) and wide area network (WAN) interface cards. As a result, multiple LAN and WAN media are simultaneously and interchangeably supported by simply changing interface cards inserted into the slots of the enclosure. The modular meter based utility gateway enclosure includes a WAN card slot for accepting a WAN interface card, multiple LAN card slots for respectively accepting LAN interface cards, and a data bus for enabling communication between the WAN interface card and the LAN interface cards inserted into the WAN and LAN card slots respectively. The modular meter based utility gateway enclosure may also support one or more interdiction cards, and may further include a tamper proof mechanism to prevent unauthorized tampering with the enclosure.

Abstract: A distribution system architecture provides a platform for communicating energy services and non-traditional services as part of an overall communications infrastructure. A native message, regardless of the source of the message's application, is divided into data packets that are encapsulated and transmitted through an open network from a headend to a gateway or from the gateway to the headend. The receiver of the encapsulated data reassembles the original native message from the encapsulated data packets. The encapsulating information can include a header which incorporates a time division multiple access transport scheme. The encapsulating information at the headend provisions the gateways from the headend in a real time fashion and the headend dynamically allocates the gateway functions of listening, talking and acknowledging.

Abstract: An optical modulator for a high power laser transmitter includes a laser source coupled through a phase modulator to a signal modulator. A noise source provides a band limited noise signal to either the laser source or the phase modulator or both. Alternatively, an optical modulator for a high power laser transmitter includes a laser source providing a laser output optical signal and a phase modulator. First and second continuous wave signals at respective first and second frequencies are combined to modulate either the laser source or the phase modulator. The first frequency is different than the second frequency. The laser and phase modulation produces a broadened optical output signal such that the broadened optical output signal is characterized by beat frequencies harmonically related to the first and second frequencies. The modulation bandwidth includes no significant beat frequencies.

Abstract: A communication loop using a subscriber line interface circuit (SLIC) is modified such that it can operate in unbalanced ringing environments as well as balanced ringing environments. This is accomplished by grounding the tip lead of a telephone instrument and creating an open circuit at the tip lead of the SLIC. The ring lead of the telephone instrument and the ring lead of the SLIC are electrically connected, and an AC voltage applied to the ring lead by the SLIC is increased. A power supply is connected to the SLIC and biased to provide the increased AC voltage on the SLIC ring lead while the average voltage on the SLIC tip lead is maintained substantially at ground. The result of this circuitry is a trapezoidal signal meeting the amplitude, loading and crest factor requirements of Bellcore Technical Requirement Publications TA-NWT-000909 and TR-NWT-000057.

Abstract: The present invention discloses a method and apparatus for providing very fast message synchronization of synchronous serial data streams by reducing system reliance on complex and highly computational synchronization schemes. The benefits of the instant invention are realized by performing most of the computational effort during message design, rather than during real-time detection. The synchronization pattern preceding the data stream is constructed in accordance with predetermined rules and compared using multiple bit segment compares rather than performing comparisons bit-by-bit. The synchronization pattern is further provided with an index that is used to access a lookup table that contains information for providing true alignment of the data stream once synchronization has been detected.

Abstract: A control system provides secure transmission of programs, including at least one of video, audio, and data, between a service provider and a customer's set top unit over a digital network. Program bearing data packets are recieved in a first network protocol over a first data link and removed from the first network protocol. Packets representing a particular program requested by a customer having a set top unit are selected. Conditional access is provided to the selected program. In particular, program bearing packets are encrypted according to a first encryption algorithm using a first key, which is then encrypted according to a second encryption algorithm using a second key. The first keys are transported in packets to the customer's set top units along with the program packets. A public key cryptographic technique encrypts the second key such that the public key used in the encryption corresponds to the private key of the customer's set top unit.

Abstract: A data communications protocol for single path media having low data error rate requires the generation of a data packet with a start code field having a predetermined pattern, a byte count field for defining a data field having a maximum predetermined length in bytes, a data payload field having a byte count according to the value of the byte count field and a cyclic redundancy check field of predetermined length. The value of the byte count field may be fixed, may be changed from packet to packet or may be changed upon initialization. The described data communications protocol permits utilization with data types varying from high definition television to alarm reporting applications. Moreover, the data rate may be varied by varying an idle time signal duration up to a maximum (when the idle time signal duration is reduced to zero).

Abstract: A hybrid fiber coax communications system includes plural coaxial distribution plants, fiber optic nodes, fiber optic links and a headend. At least one subscriber is coupled to each coaxial distribution plant. In the upstream signal path, the upstream signals travel from the coaxial distribution plants to the fiber optic nodes and through the fiber optic links to the headend. In the headend, optical receivers receive each upstream signal and pass the signals to respective node switches. The node switches selectively connect the upstream signals to a demodulator. An element control manager provides a control signal to the node switches to control whether the switch is in an open or closed state. One of the switches can be selected to be closed so that the demodulator receives one of the upstream signals.

Abstract: A method and system for distributing multimedia signals to a subscriber from a headend unit. The multimedia signals are transmitted on a network media as an RF signal. The RF signal is fed to an input terminal of a tap which has an RF circuit that splits the RF signal and distributes to an output terminal. The RF circuit splits the RF signals, and feeds the split signal to a plurality of connectors on the tap's front panel. The RF signals on the output terminal are fed downstream to a plurality of subscribers. A plate is placed in the tap such that when the RF circuit is removed for repair, maintenance or service, an electrical connection is maintained between the input and output terminal to prevent a disconnection of service downstream.

Abstract: A communication system, such as a cable television system, includes an optical transmitter (FIG. 2) that includes adaptive predistortion control circuitry (104). The adaptive predistortion control circuitry (104) measures the distortion produced by television band signals processed in the communication system. In the optical transmitter (FIG. 2), the distortion signal produced by the television signals is a relatively high-level signal from which necessary predistortion control signals may be more easily processed. Additionally, the adaptive predistortion control circuitry (104) detects both the amplitude and the polarity of distortion within the optical output (FIG. 2) of the optical transmitter, which enables the control circuit (104) to determine the correct polarity and level adjustments that should be made to the predistorter (102) included in the optical transmitter.

Abstract: A cable television system employs two-way communication between a headend and at least one subscriber terminal. The two-way communication is provided by having separate frequency bands for each communication path. The frequency bands do not overlap and the higher frequency band is used for subscriber terminal to headend transmissions. A line amplifier is provided that employs two diplex filters each connected to both a forward and reverse amplifier. The high pass portions of the diplex filters are formed from both lumped and distributed components.

Abstract: A multi-channel modulator for the transmission of telephony signals within a broadband communication system. An interpolation module generates processed I and Q signal components by upsampling filtered I and Q signal components. In turn, these processed I and Q signal components output by a filter are passed to a set of channel modulators. Each channel modulator accepts a pair of processed I and Q signal components and, in response, modulates a selected carrier signal with one of the telephony signals to produce a complex modulated signal. An adder module responds to the complex modulated signals by summing the real signal components to produce a real resultant signal, and to sum the imaginary components to produce an imaginary resultant signal. A digital-to-analog converter (DAC) module coverts the real resultant signal and the imaginary resultant signal, which are represented by digital data streams, to analog signals.