3com Corporation

Hewlett-packard Development Company, L.p.

U.S. Robotics Mobile Communications Corp.

John P Evans

Spiro Poulis

Shayne Messerly

Tim Urry Price

Thomas A Johnson

Ryan A Kunz

Steven Lo Forte

James B Henrie

Sprio Poulis

Shane Messerly

Minh Truong

Nicholas A Thomas

Richard Bentley

Mark L Gray

The present invention discloses circuits for isolating and attenuating signals generated by a telephone network. In disclosed embodiments, a metering pulse signal is isolated from the terminals of the connecting device, and then attenuated with an impedance that is synthesized with a programmable digital signal processor. Embodiments also utilize the digital signal processor to synthesize a termination impedance for the connecting device. The termination impedance matches closely the characteristic impedance of the network, so as to minimize wave reflections and the like.

Attenuation and termination circuit using impedance synthesis

The present invention synthesizes a prescribed impedance. The impedance is synthesized by generating a current having a value substantially equal to a voltage divided by a prescribed impedance. Sensing the line voltage and converting that sensed line voltage to its digital equivalent accomplish this first step. The digital line voltage is processed by a factor related to the prescribed impedance to produce an output voltage that has a value substantially equal to the sensed voltage divided by the prescribed impedance. The output voltage controls a voltage to current converter that generates the appropriate current across the points or terminals where the line voltage was measured. Thus, the prescribed impedance is generated across these points or terminals because the line voltage divided by the generated current is substantially equal to the prescribed impedance.

Systems and methods for impedance synthesis

The present invention provides apparatus and methods for attenuating signals received from a source over a data transmission line, having an unknown resistance, to achieve optimized signals in various data terminal and data communications equipment. In a preferred embodiment, a resistor network is operably coupled between the transmission line and a means for processing the signal, such as a digital processor, an ADC and a DAC. The resistor network comprises a termination resistor that is associated with a termination voltage, a variable resistor and another resistor. During use, a switch is operably positioned between a plurality of switch positions so that two voltage measurements will lead to the determination of the voltage of the source and the termination voltage within the resistor network. Once these voltages are known, the unknown resistance can be estimated. Thereafter, the length of the transmission line may be determined because of known resistance-per-unit-distance characteristics of the transmission line. In response to knowing this length, the digital processor selects a desired resistance value for the variable resistor so that, upon adjustment of the variable resistor by the DAC, the signal becomes a largest-possible input at the ADC.

Data signal attenuator and systems and methods for using same

Provided is a circuit for terminating a ring signal of a telephone network. A physical impedance is combined with a synthesized impedance to produce an impedance having a magnitude substantially equal to the ring termination impedance of a telephone network. The synthesized impedance is created by generating a current from a voltage controlled current source. By controlling the magnitude of the generated current, the magnitude of the synthesized impedance is also controlled. Because the specified ring termination impedances are known, a satisfactory impedance can be synthesized which results in the ring signal being properly terminated.

Synthesized telephone line ring signal impedance termination

The present invention provides a line termination circuit for matching the characteristic impedance of a transmission line, or more generally, a network. The present invention receives the voltage as present on the transmission line and attenuates it such that circuit components rated for lower voltages may be used to produce the reflected impedance. The attenuated voltage is placed across a scaled impedance which results in a reflected impedance substantially equal to the characteristic impedance of the transmission line. The line termination circuit uses a feedback loop to reflect the ground referenced scaled impedance across the transmission lines. The circuit generates a current having a value of one over the characteristic impedance of the network, which ensures that the reflected impedance, from the network, is substantially equal to the characteristic impedance of the network.

System and method for terminating a line by reflecting a scaled impedance

A retractable platform allows communication to be established with an electronic device, such as a computer expansion card. The retractable platform is preferably slidably attached to the electronic device and retractable platform includes a wireless interface that allows the communication between the platform and the electronic device to be established. The wireless interface may use an optical coupling, inductive coupling, capacitive coupling or other suitable wireless or non-mechanical interface to allow communication between the retractable platform and the electronic device. Advantageously, the retractable platform can be removed and replaced, which virtually eliminates breakage, and it allows the platform to be easily repaired, replaced, upgraded, and the like. The retractable platform can also include electronic circuitry and other suitable components that process or condition the incoming and outgoing signal.

Retractable platform with wireless electrical interface

A circuit is provided for creating a termination impedance which matches a characteristic impedance. The characteristic impedance of a system or network is matched by placing a nominal impedance across the transmission line. The difference between the nominal impedance and the characteristic impedance is synthesized such that the synthesized or generated impedance is in parallel with the nominal impedance. The parallel combination of the nominal impedance and the generated impedance produces a termination impedance which substantially matches the characteristic impedance. The generated impedance is created by sensing a voltage and scaling that voltage by a factor related to the nominal and characteristic impedances. The scaled voltage controls a current source which produces a current having a value related to the inverse of the impedance. The ration of the sensed voltage and the generated current is the impedance which, when combined with the nominal impedance, produces the desired termination impedance. In this manner, the characteristic impedance of the source is matched by the altered nominal impedance.

Partial modification of a nominal impedance using digital impedance synthesis

A power management circuit for use in a terminal interface device such as a modem which converts available power from a terminal or host device such as a computer into usable standby power for use when the terminal interface device is non-operational. The power management circuit is additionally comprised of a voltage regulator which, when a terminal interface device becomes operational, is enabled and regulates available voltage and current into usable power as available from the interfacing communication network. The preferred embodiment of the power management circuit is further comprised of a programmable hold current generator which enables a terminal interface device incorporating the power management circuit to be compatible with multiple communication networks having diverse hold current specifications. The use of power available from the communication network in generating the operational voltage greatly reduces interference injected onto the communication network.

Telephone line-assist powered apparatus with programmable hold current

A system and circuit is provided for digitally synthesizing the impedance of a transfer function. The impedance of the transfer function is digitally synthesized by generating a current that, when combined with an input voltage, results in the impedance of the transfer function. This is accomplished by sensing the input signal and processing it with a generator or multiplier such that a voltage is produced. The produced voltage controls a current source and creates a current having a value equal to the inverse of the transfer function impedance. The sensed or input voltage divided by the generated current is equal to the impedance of the transfer function. In this manner, many different transfer functions can be digitally synthesized without having to design an alternate circuit.

Transfer function implementation using digital impedance synthesis

A method and apparatus for automatically switching between voice and data communications as directed by a voice and data capable modem via a cable assembly incorporating a switching means for facilitating and inhibiting the routing of voice information to a voice telephone. A voice and data capable modem incorporates the software functionality associated with a voice and data capable protocol with minimal impact to the form factor associated with the modem, To reduce the impact to the form factor associated with integrated modem designs, the switching hardware associated with voice and data capability is incorporated into a cable assembly used to interconnect the voice and data capable modem with the voice telephone. Additional means for identifying the cable assembly as having the requisite switching functionality is also provided.

Method and system for externally incorporating automatic switching between voice and data communications

A jack for facilitating an electrical communication between a media plug and an electrical apparatus includes a low profile slide plate having an aperture extending therethrough. The aperture is configured to receive a media plug. A contact pin projects from the slide plate into alignment with the aperture and is configured to engage the media plug in electrical communication when the media plus is received within the aperture. Mounted on the slide plate is a pair of spaced apart first and second fuse contacts. The fuse contacts are configured to receive and retain a fuse disposed therebetween. The first fuse contact is disposed in electrical communication with the contact pin. The second fuse contact is configured for electrical coupling with the electrical apparatus. In one embodiment, the first and second fuse contacts are disposed within a fuse slot formed on the slide plate. The slide plate can be configured for either permanent or removable attachment to the electrical apparatus.

Media jack with external fuse access

A selectively removable module, such as a PCMCIA card, inserted into a host computer system, such as a notebook computer, is provided that has a electrical interface between the module circuitry and the host computer circuitry, A wireless data channel is implemented between the module circuitry and the host computer system circuitry that is independent of the electrical interface. This wireless communications channel is implemented entirely within the confines of the external housing of the host computing system. One embodiment uses an infrared LED or emitter to transmit infrared signals from the module circuitry to an infrared sensitive phototransistor located within the host and electrically connected to the host circuitry. Likewise, an infrared LED or emitter located within the host computer housing and electrically connected to the host computer circuitry transmits an infrared signal to a infrared sensitive phototransistor located on the module and electrically connected to the module circuitry to complete a bi-directional, wireless data transmission channel. The internal wireless data transmission channel allows large data throughput without interfering with the operation or capacity of the normal electromechanical interface between the module circuitry and the host computer system. Such a wireless data communications channel finds particular use in implementing a speakerphone on a host computer system, such as a notebook computer, having a microphone and speaker but using the circuitry in a PCMCIA modem card to manage and control the speakerphone.

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Riverton, UT, United States of America

John P Evans