Abstract: An improved surge protection circuit for withstanding surges is provided. A first node is provided for coupling to a tip lead, and second node is provided for coupling to a ring lead. The surge protection circuit has a first current path for turning on a first transistor, and a second current path for redirecting current from the remaining excess surge energy from one lead to the other lead. The first current path further includes a first sub-path to direct the initial voltage surge to the base electrode of the first transistor to cause the first transistor to turn on hard. The second sub-path redirects current from the initial excess surge energy from the voltage surge to a capacitor prior to the time before the first transistor is fully turned on, so as to protect the base-emitter junction of a second transistor from being reverse biased.

Abstract: A frequency conversion or synthesis circuit including a double balance differential active ring mixer with a current shared active radio frequency (RF) input balun, suitable for use in an RF receiver. The circuit is configured to be coupled to a bias circuit for providing a relatively constant current and a buffer circuit for receiving a signal from a local oscillator (LO) source and generating differential LO signals.

Abstract: A DC voltage power supply for a time division multiple access (TDMA) radio system is provided. The DC voltage power supply apparatus includes an AC signal source, a switching transistor, a controlling signal source, a voltage converter circuit, and a capacitor. The AC signal source provides an AC signal to the DC voltage power supply. The switching transistor is coupled to the clock for switching on and off the clock signal. The controlling signal source is coupled to the switching transistor for turning the switching transistor off during a transmission or reception period and for turning the switching transistor on during an idle period. The voltage converter circuit is coupled to the switching transistor and generates a DC output voltage from the AC signal. Finally, the capacitor is coupled to the voltage converter such that the capacitor is charged by the DC output voltage when the switching transistor is turned on and the capacitor holds the DC output voltage by discharging when the switch is turned off.

Abstract: A method and apparatus for compressing and transmitting variable amounts of video data in real time over a channel having a fixed bandwidth. A trellis having a plurality of nodes is provided. Each of the plurality of nodes has an associated quantization parameter and bit number. The bit number associated with each node corresponds to a quantity of bits consumed in reaching that node. For each of the plurality of blocks, a minimum path through the trellis is selected. A quantization parameter associated with the selected minimum path is selected. A number of bits is assigned to each of the plurality of blocks in accordance with the selected quantization parameter. A substantially fixed number of bits is distributed among the plurality of blocks which make up each of the plurality of frames in accordance with the selected quantization parameter.

Abstract: A method and apparatus for a spread spectrum matched filter with Doppler correction suitable for using in a radio frequency receiver. A principal idea of the invention is to reduce a waveform representing Doppler correction values into a simple Boolean combination that can simply represent the waveform and be built into the processing in the matched filter. Advantages are (1) faster use of the matched filter, resulting in faster signal acquisition, and (2) lower power consumption because clocking to load signal and/or Doppler correction values is reduced. In particular, received samples can be Doppler corrected for the nominal or mean Doppler shift plus local oscillator error as they are stored. The remaining Doppler shift is relatively small and can be removed by building a relatively few Doppler offsets into the processing logic for each matched filter tap. This saves time because the Doppler shift can be changed almost instantly.

Abstract: A power management system for a mobile station reduces standby mode processing by receiving and processing single time slots of a short paging channel. Each single time slot of a short paging channel includes a mobile station identifier which alerts a receiving mobile station that a pending telephone call or paging message may be directed to the mobile station. Once so alerted, the mobile station receives and processes full paging channels comprising four time slots to determine whether the mobile station is the intended recipient of the telephone call or paging message. If the mobile station determines that it is not the intended recipient, then the mobile station resumes receiving and processing single time slots of the short page channel. Processing fewer time slots of data for purposes of call detection conserves mobile station battery power.

Abstract: A method and apparatus are claimed that separate network-dependent from network-independent functions in set-top boxes (STBs), including digital consumer appliances and PCs. A receiver subsystem integrates network-dependent tuner, digital demodulation, Forward Error Correction (FEC), descrambling/decryption, and conditional access functions into a very small format (e.g., any of the PCMCIA Type I, II, or III form-factor). This combination of functions comprises a Digital Interface Conditional Access Module (DICAM). The DICAM interfaces with a Set-Top Universal Box (STUB) that includes network-independent functions. The STUB functionality may also be integrated with a consumer electronics (CE) appliance such as a TV, PC, DVD player, etc. The DICAM may also include an interface for "Smartcards" that implement any of the many different varieties of CA functions currently found around the world.

Abstract: The AGC circuit and method especially applicable in circuits where fast response and stability of the system is necessary, such as where input signals are speech patterns. A gain feedback loop repeatedly adapts the gain and a long term average energy E.sub.mean of the output signal until it approaches a predetermined level. In each pass through the gain feedback loop the long term average energy E.sub.mean is increased by a gain compensation parameter directly proportional to a gain change, thereby rapidly adapting the long term average energy E.sub.mean to converge to the predetermined level.

Abstract: The present invention relates to multiple modulus conversion (MMC) techniques for mapping data in a pulse code modulation (PCM) modem system. In accordance with the present invention, signal point constellations are arranged to receive the output indices generated by the MMC procedure such that the probability of transmission of higher power codewords is relatively low compared to the probability of transmission of lower power codewords, while maintaining the same or larger minimum distance between signal points. In addition, the present invention provides techniques for obtaining the probability of occurrence for each constellation or signal point associated with a given data communication session and for determining the theoretical average transmit power associated with a given set of signal point constellations and MMC parameters.

Abstract: An improved battery management circuit and system are disclosed. The improved battery management system relates to the type having at least one battery cell that is connected in a circuit with battery powered components, a current sensing resistance that is located in series within the circuit, voltage measurement circuitry that measures the voltage that develops across the current sensing resistance in proportion to the current flowing through the resistance, a cutout switch that is located in series within the circuit, and means for opening the cutout switch when the measured voltage is too high. The improvement is a single circuit element which functions as the current sensing resistance and as the cutout switch, the single circuit element having first and second electrodes and a control electrode that turns the first and second electrodes "on" and "off" and wherein the current sensing resistance is an on-resistance between the first and second electrodes.

Abstract: The invention's reference precharge circuit and bit line precharge circuits are comprised of two NFET transistors and one PFET transistor. In the preferred embodiment of the invention where the supply voltage is 3.0 volts, the two NFET transistors result in a voltage drop of 2.0 volts so as to produce a reference precharge signal or a bit line precharge signal having a voltage of 1.0 volts. When a precharge enable signal is on, the PFET transistor is connected to ground and is barely on such that the path from the reference precharge signal or the bit line precharge signal to ground is a low impedance path. Moreover, the path from the reference precharge signal or the bit line precharge signal to the supply voltage is also of low impedance. Accordingly, the voltages present at the reference precharge signal or the bit line precharge signal are substantially noise free.

Abstract: A pulse code modulation modem system is configured to transmit data from a first modem to a second modem over the public switched telephone network (PSTN). The PSTN employs robbed bit signaling (RBS) such that symbols affected by RBS arrive at the second modem in a periodic manner based on a period of six symbols. The modem system is configured such that signal segments are formatted and transmitted with six symbols per segment. After obtaining symbol synchronization, the second modem initializes a modulo-6 symbol counter such that the zero count corresponds to the first symbol of each received signal segment. Those symbols affected by RBS are identified and analyzed to determine optimized signal point constellations that may be used to compensate for the RBS on a symbol-by-symbol basis during subsequent encoding and decoding. Upon a loss of synchronization, the second modem resets its modulo-6 counter in response to the detection of the first symbol in a subsequent signal segment.

Abstract: A synthesizer system includes a CPU and host memory operating a software routine. The software routine stores a first part of each waveform signal in a sample pool of host memory and provides remaining portions of selected musical sounds from the hard drive to a stream cell array without an audio perceivable delay. The synthesizer system utilizes a caching system which allows low cost, high storage devices to be utilized in an audio synthesizer system. MIDI control signals are provided to an audio processor for selecting appropriate digital waveform signals.

Abstract: A transformer driver circuit connected to the primary or "system" side of a transformer has a system clock connected to an input thereof the system clock having a frequency selected to constitute the desired clock frequency of a CODEC circuit located on the secondary or "line" side of the transformer. A signal line is connected to a point on the secondary of the transformer so as to tap the system clock frequency, whereby both the system clock and the source voltage for the CODEC are derived from the transformer's secondary.

Abstract: A frequency synthesizer for generating two or more output frequency ranges using a Phase Locked Loop (PLL) circuit having a single voltage-controlled oscillator (VCO). In a first embodiment, a frequency multiplier is connected to the output of the VCO. The output of the VCO and the output of the frequency multiplier are selectably fed back, depending upon which output frequency is desired. The output frequency may be taken directly from the VCO or the frequency multiplier. When the output frequency is taken from the output of the frequency multiplier, a control signal adjusts the gain of the phase detector and/or loop filter in order to compensate for the loop gain caused by the frequency multiplier. In a second embodiment, instead of adjusting the phase detector and/or loop filter gain, the values of the N and M dividers are adjusted. In a third embodiment, a frequency multiplier is connected to the output of the VCO and multiplies the output by a predetermined multiplier value.

Abstract: A full-featured data access arrangement (DAA) for connecting a modem to a public switched telephone network (PSTN) includes a bridge current loop circuit, a line in use detection circuit, an off hook relay, a loop current sense circuit, and an extension/remote event detector circuit. The off hook relay is connected in series with the current loop circuit to enable the DAA to detect external off hook and on hook events when the modem is in an on hook state. The DAA is configured to detect the off hook and subsequent on hook status of an extension telephone at a location even though the modem and a handset sharing a line connector with the modem are both in an on hook state. The DAA is also capable of detecting an off hook state of an extension telephone even though the modem is in an off hook state. In addition, the DAA can detect when a remote telephone device that initiates an incoming call is placed on hook.

Abstract: An asynchronous transfer mode scheduler schedules connection utilizing available bit rate (ABR) modes of traffic, unspecified bit rate (UBR) modes of traffic, variable bit rate (VBR) modes of traffic, and constant bit rate (CBR) modes of traffic. The scheduler communicates with a dynamic schedule table which includes a programmable number of slots. Each slot includes a CBR entry, a tunnel entry, and a number of VBR entries. The VBR entries store a slot tail pointer which indicates the end of a linked list. The scheduler utilizes the single bucket algorithm or dual bucket algorithm to dynamically schedule connections on future slots. The scheduler places connections using the VBR mode of traffic in a priority queue and takes the highest priority connection in the priority queue for transmission on the network.

Abstract: The present invention comprises a smart subscriber line interface card (SLIC). The SLIC of the present invention includes a switch coupled to a data transmitter, a DAC (digital to analog converter), and a controller circuit. The data transmitter is coupled to a first input of the switch and is adapted to generate a data transmitter output from a received digital network signal and couple the data transmitter output to the first input of the switch. The DAC is coupled to a second input of the switch and is adapted to generate a DAC output from the received digital network signal and couple the DAC output to the second input of the switch. The controller circuit is coupled to the switch and functions by configuring the switch for either efficient data transmission via the data transmitter, or conventional communication via the DAC.

Abstract: A multi-communication rate switching physical device for a port of a mixed communication rate Ethernet repeater network. The present invention includes a physical device for recovering bits from a wire connection (e.g., fiber, twisted pair, etc.) that is coupled to computer system adapter. The physical device can be implemented on a single chip integrated within an Ethernet repeater hub within each hub port. The physical device chip of the invention includes a front end multiplexer coupled to channel information between a 10 Base T physical device circuit and a 100 Base T physical device circuit, depending on the result of an auto-negotiation circuit also on the physical device chip. The physical device chip also advantageously employs a second, back end multiplexer, that is coupled to channel data between either the 10 Base T physical device circuit or the 100 Base T physical device circuit and one of a multiple of media independent interfaces (MIIs).

Abstract: An ATM system transmits different types of cells (data, forward resource management (RM) and backward RM) from station A through switch(es) to station B. Different fields in an Available Bit Rate (ABR) table provide controls over the rate of such cell transmissions. First particular field values in such table control the selection of successive ones of cell decision blocks which determine the type of cell to be transmitted. Second particular field values in such table control the selection of one of a plurality of entries in an exponent table which also provides other parameter values controlling the generation of an explicit rate. Third particular field values in the ABR table control the selection of an individual one of a plurality of rate decision blocks each indicating an individual rate of cell transmission from the station A to the station B.