Abstract: A hook switch circuit is shown wherein two high-voltage bipolar transistors, a PNP transistor Q1 and a NPN transistor Q2. that are connected in a regenerative feedback manner to form a bi-stable latch. The regenerative structure permits the use of low beta transistors that may be turned on with a low control current, but still conduct a sufficient off-hook current. Also shown is a polarity steering regenerative switch (MP1, MP2) that provides a power supply voltage from a telephone line pair and may be adapted for a polarity signal and can be combined with a current mirror (MP7) to produce a current signal proportional to the line voltage (LV1).

Abstract: Transmitter and receiver circuits are shown that are capable of operating in a stand-alone mode without the necessity of an external controller to program the transmitter and receiver circuits, such as by providing operating parameters through a control interface. An internal controller of the transmitter detects that no external controller is present and operates to access an external storage device, such as an EEPROM, to obtain data for configuring at least some of the operating characteristics of the transmitter. The transmitter may be configured to respond to predetermined events by accessing corresponding data at predetermined addresses of the EEPROM. The internal controller of the receiver may also detect that no external controller is present and to obtain data for configuring at least some of the operating characteristics of the receiver.

Abstract: A distributed photodiode structure is shown formed on a semiconductor substrate having a first dopant type where a first plurality of diffusions of a second dopant type are formed on a first surface of the substrate. A second plurality of diffusions having the first dopant type are formed on the first surface of the substrate between the first plurality of diffusions. In a further refinement, a second surface of the substrate is diffused with the first dopant type. In yet another refinement, a plurality of trenches are formed on the first surface and the second plurality of diffusions are formed within the trenches.

Abstract: A PIN photodiode and method for forming the PIN photodiode are shown where an intrinsic layer of the photodiode can be made arbitrarily thin and a second active region of the photodiode substantially shields a first active region of the photodiode. A fabrication substrate is lightly doped in order to form the intrinsic layer of the photodiode. A void is formed in a first surface of the fabrication substrate and a first active region of the photodiode having a first conductivity type is formed in the void. An oxide layer is also formed upon the first surface of the fabrication substrate. A handling substrate is bonded to the first surface of the fabrication substrate. A second surface of the fabrication substrate is then lapped to a obtain a preselected thickness of the intrinsic layer. A depth of the void is selected such that a portion of the first active region is exposed at the second surface of the fabrication substrate after lapping.

Abstract: A circuit and method are shown for battery reversal protection. The circuit includes a first transistor that buffers a bulk terminal of a protected transistor from an input terminal for receiving a power supply voltage. A second transistor is coupled to both the input terminal of the circuit and an output terminal of the circuit and detects when the power supply voltage falls below an output voltage at the output terminal and, responsive thereto, switches off the first transistor to isolate the bulk terminal of the protected transistor from the input terminal. Another aspect of the invention provides current reversal protection using a third transistor that also detects when the power supply voltage falls below an output voltage at the output terminal and, responsive thereto, conducts current from the output terminal to the gate terminal of the protected transistor.

Abstract: The present invention is directed toward a method and apparatus for transferring data across an isolation barrier using high speed analog encoded signals. A line side circuit interfaces with tip and ring contacts on one side of a capacitive isolation barrier that isolates the line side circuit from a modem side circuit. During an on-hook state, the line side circuit converts an analog line side voltage signal to a frequency signal and then encodes the frequency signal into a high frequency pulse-width-modulated (PWM) signal. The high frequency PWM signal is transmitted across the capacitive isolation barrier to the modem side circuit. During an off-hook state, the analog line side voltage is again encoded into a high frequency pulse-width-modulated (PWM) signal for transmission across the isolation barrier. The modem side circuit recovers the transmitted PWM signal and converts it into a digital count value that represents the amplitude of the analog voltage observed at the tip and ring.

Abstract: A method and apparatus are shown for integrating a photodiode and a receiver circuit on a single substrate. An input signal is received with the photodiode. The receiver circuit is configured to suppress feedback from an output terminal of the receiver circuit to the photodiode by amplifying the input signal to produce an amplified input signal, controlling the gain of the input signal amplification responsive to the magnitude of the amplified input signal, comparing the amplified input signal to a detection threshold voltage to produce a digital data signal, and holding the gain at a substantially constant level in response to a fast signal transition in the digital output signal.

Abstract: A method is shown for producing a distributed PN photodiode having a first active region of the photodiode that can be made arbitrarily thin. A fabrication substrate is doped to have a first conductivity type in order to form the first active region of the photodiode. A layer can also be formed upon the first surface of the fabrication substrate or a first surface of a handling wafer, where the layer can be an oxide layer, where a thickness of the oxide layer can be controlled to form a dielectric refractive reflector, a reflective layer, or a conductive layer. The first surface of the handling substrate is bonded to the first surface of the fabrication substrate. A second surface of the fabrication is then lapped to a obtain a preselected thickness of the first active region. A plurality of second active regions of the photodiode having a second conductivity type is formed on the second surface of the fabrication substrate.

Abstract: A method and apparatus are shown for integrating a photodiode and a receiver circuit on a single substrate. An input signal is received with the photodiode. The receiver circuit is configured to suppress feedback from an output terminal of the receiver circuit to the photodiode by amplifying the input signal to produce an amplified input signal, controlling the gain of the input signal amplification responsive to the magnitude of the amplified input signal, comparing the amplified input signal to a detection threshold voltage to produce a digital data signal, and holding the gain at a substantially constant level in response to a fast signal transition in the digital output signal.

Abstract: Disclosed is a method and apparatus for receiving infrared signals that is better able to receive a data signal in the presence of a noise signal. The method according to the present invention involves bandwidth filtering an incoming signal that includes a data signal and a noise signal. The bandwidth filtered signal is then averaged to obtain an average alternating current (AC) value signal of the bandwidth filtered signal. The average AC value signal is integrated to obtain a detect level adjustment signal. The detect level adjustment signal is summed with a minimum detect threshold value to obtain a detection level signal. The incoming signal is then compared to the detection level signal in order to produce a received data signal.

Abstract: A method and apparatus are shown for integrating a photodiode and a receiver circuit on a single substrate. An input signal is received with the photodiode. The receiver circuit is configured to suppress feedback from an output terminal of the receiver circuit to the photodiode by amplifying the input signal to produce an amplified input signal, controlling the gain of the input signal amplification responsive to the magnitude of the amplified input signal, comparing the amplified input signal to a detection threshold voltage to produce a digital data signal, and holding the gain at a substantially constant level in response to a fast signal transition in the digital output signal.

Abstract: A method and apparatus is shown for controlling the input gain of a receiver wherein the input gain is controlled by sampling an amplified data signal during a time interval when a positive-going feedback transient from an output terminal of the receiver to an input terminal of the receiver is not present in the amplified data signal. An embodiment of a receiver circuit according to the present invention includes an input amplifier having variable gain determined by a gain control signal, a comparator which compares the amplified data signal from the input amplifier to a detection threshold voltage to produce a demodulated data signal and an analog delay circuit which delays the amplified data signal by a predetermined time interval to produce a delayed data signal. A switch is driven by the demodulated data signal to sample the delayed data signal for input to an automatic gain control circuit.

Abstract: A distributed photodiode structure is shown having a plurality of diffusions formed in a uniform pattern on a first surface of a semiconductor substrate and interconnected by a plurality of connective traces. The diffusions are minimum geometry dots for a standard semiconductor fabrication process that are spaced apart from one another by an interval that is less than an average distance travelled by photo-generated carriers in the substrate before recombination. A conductive backplane is formed on a second surface of the semiconductor substrate to produce an inverted induced signal for noise cancelling.

Abstract: An output signal pulse width error correction circuit and method wherein errors in a data signal conforming to a communications protocol having a prescribed duty cycle are corrected by monitoring a duty cycle of the data signal, comparing the duty cycle to a duty cycle reference voltage corresponding to the prescribed duty cycle, and adjusting a pulse width of the data signal to conform to the prescribed duty cycle of the protocol. An embodiment is shown that low pass filters the input data signal to introduce greater slope to the input data signal which is then compared to a pulse width control voltage in order to generate an output data signal. The pulse width control voltage is produced by integrating the output data signal to obtain an average value corresponding to the duty cycle of the output data signal and comparing the average value to a duty cycle reference voltage corresponding to the prescribed duty cycle for the communications protocol.

Abstract: A data access arrangement generates a first current in a first current path which runs from a tip terminal of a line pair through a light emitting diode of an opto-isolator to a sense node. The data access arrangement also generates a second current in a second current path that runs from the tip terminal to the sense node. The first current is modulated in response to an audio input signal received from the telephone line pair, while the second current is modulated in response to a potential generated at the sense node, such that a third current flowing from the sense node to the ring terminal remains at a substantially constant predetermined magnitude.

Abstract: A receiver circuit and method wherein an automatic gain control circuit of the receiver is isolated from the input to the receiver in response to the output signal from the receiver in order to suppress the effect of feedback from the output signal to the input of the receiver.

Abstract: An internal telephone intercom system including means for connecting to a dedicated telephone communication line, a plurality of telephone sets connected to the line and adapted for telephone communications with locations external to said dedicated line, an audio receiving means at each telephone set for receiving audio signals from a microphone within said telephone set, a radio frequency generator means for generating a carrier frequency and amplitude modulated responsive to said audio signals with said modulated signal being multiplexed on said dedicated line, an audio expander for receiving a modulated signal from the radio frequency generator means and producing an audio signal responsive to audio sounds at a speaker.

Abstract: A telephone activated power controller comprised of an electrical power inlet and a number of power outlets for supplying power to the devices of a computer or other system. A detection circuit detects telephone rings and off-hook conditions and powers up the system. A remote control circuit allows the computer to keep the power on after hang-up or manual power-off. A status sensor circuit tells the computer if the device has been turned on manually or remotely. An inhibit circuit prevents the device from responding to a telephone ring or off-hook condition if it is engaged. The controller also has a surge protection circuit to prevent large voltages or current from reaching the power outlets.

Abstract: A transmission system develops a binary encoded data train having a message and a header preceding the message. The data train is applied to a carrier frequency to modulate the carrier using FSK techniques. The header includes synch signals, one or more address signals, a message length signal and control signals separating the above signals. One or more personal receivers receive the message if responsive to one of the address signals in the header. An address signal may address a unique personal receiver, a selected group of or all such personal receivers. Each receiver is sequentially activated and deactivated, being activated to detect a synch signal. If synch signals are detected, the receiver remains activated to determine if an address signal identifies such receiver to receive the message. A received message is stored digitally in a number of storage locations determined by the message length signal and may be selectively displayed in alphanumeric characters when convenient for the recipient.

Abstract: A transmission system develops a binary encoded data train having a message and a header preceding the message. The data train is applied to a carrier frequency to modulate the carrier using FSK techniques. The header includes synch signals, one or more address signals, a message length signal and control signals separating the above signals. One or more personal receivers receive the message if responsive to one of the address signals in the header. An address signal may address a unique personal receiver, a selected group of or all such personal receivers. Each receiver is sequentially activated and deactivated, being activated to detect a synch signal. If synch signals are detected, the receiver remains activated to determine if an address signal identifies such receiver to receive the message. A received message is stored digitally and may be selectively displayed in alphanumeric characters when convenient for the recipient.