Motorola Corporation

Adtran Gmbh

Other

Universal Data Systems, Inc.

David Paul Nelson

Joseph L Harris

Steven R Blackwell

Charles E Polk, Jr

David H Nabors

David E Wilder

Richard A Beichler

A redundant communication system contains a principal transceiver and a back-up transceiver to be controllably substituted for the principal transceiver. A monitor protection switch, which controls swapping the two transceivers, has an RF loopback test circuit that is switchably coupled to whichever transceiver is the back-up. The RF loopback test circuit monitors the operational capability of the back-up transceiver, and provides an indication of its functionality. If the back-up transceiver is defective, corrective action can be taken in advance of a potential operational failure of the principal transceiver. As long as the RF loopback test circuit indicates proper operational capability of the back-up transceiver, the redundant transceiver can be immediately switched in place of the principal transceiver.

Integrated RF loopback test apparatus for redundant data radio transceiver system

An RF loopback test circuit is adapted to be coupled to an antenna port of a digital radio, to determine whether the radio is functioning properly. A frequency generator outputs an auxiliary frequency corresponding to the sum or difference between the radio's transmit and receive frequencies. The auxiliary frequency is coupled to a Schottky diode mixer, which is also coupled to the input/output port. If the radio's transceiver section is operating properly, the sum or difference frequency output of the Schottky diode mixer will be passed by only the diplexer's narrowband receive path filter to the radio's receiver section. The mixer's sum frequency is blocked by the diplexer's narrowband filters. Therefore, if the receiver section provides an indication that it is receiving a sufficient signal level from the RF loopback test circuit, it can also be inferred that each of the transmitter and receiver sections is operating properly.

RF loopback test apparatus for data radio transceiver

Frequency synthesizers of a radio transceiver are automatically tuned so that its transmit and receive frequencies correspond to whichever upper band and lower band filters the radio transceiver has been connected by the user. A capacitive electrical impedance interface is coupled to filter circuitry of an upper band filter section, while an inductive electrical impedance interface is coupled to filter circuitry of the lower based filter section. A voltage reference circuit is coupled to one of the transmit port and the receive port of the transceiver. A controller is operative to automatically tune the transceiver to transmit in one of the upper and lower frequency bands, and to receive on the other frequency band, in accordance with the voltage level generated by the voltage reference circuit.

Mechanism for automatically tuning transceiver frequency synthesizer to frequency of transmit/receiver filter

An apparatus and method are provided for determining the activity status of a PCM channel in a telecommunications system. The method (600-680) and apparatus (400) utilize a codec (220) within the PCM channel which converts an analog signal to a digital signal and converts a digital signal to an analog signal. Within the apparatus (400), a memory register (402) is coupleable to the codec (220) to repeatedly obtain and store a digital byte of a plurality of digital bytes from the PCM channel. A processor (404) coupled to or containing the memory register (402) repeatedly, for a predetermined period of time, determine whether an ordered arrangement of bits of a digital byte has a predetermined bit pattern and accumulate a count of digital bytes having the predetermined bit pattern. The processor (404) then determines whether the accumulated count is greater than a predetermined value and provides a notification indicating the status of the PCM channel.

Apparatus and method for detecting the status of a PCM channel

A communication system for coupling a plurality of data terminals to a telephone network has a time division multiplexed telephone network access bus, providing a plurality of time division slots containing data, coupled to the telephone network, and a digital terminal access bus coupled to the plurality of communication devices, each communication device being configurable to access any of the time division slots. A controller for configures each communication device to access a time division slot.

Advanced communication system architecture

An improved isolation circuit for protecting data communication equipment from high voltages on a transmission line has two mixers. The first dual balanced mixer (DBMX) translates a data signal on the transmission line to a high frequency and is coupled with an isolation circuit to the second DBMX. The second DBMX then translates the output of the first DBMX to an isolated data signal with the same frequency content as the original data signal.

Line interface apparatus and method for isolating data terminal

An equalizer (100) is suitable for removing the delay distortion from a switched digital signal received from a telephone channel, where the delay distortion is caused by a bridge-tap connected to the telephone channel. The equalizer includes a feedback delay circuit (200) which is arranged to delay the output signal (150) by an amount of time based on the square of the predominant frequency of the output signal. The resulting delayed feedback signal (130) is then combined with the input signal, thereby compensating for the delay distortion. The equalizer also includes an amplifier (103) which may be adjusted to compensate for the attenuation distortion caused by the bridge-tap.

Bridge-tap equalizer method and apparatus

A bipolar return-to-zero signal received from a communication channel (302) is sampled (402) to provide signal information that is processed (FIG. 5) to determine signal variation information. In accordance with this signal variation information, at least one operational parameter of an equalization system (400) is varied.

Method and apparatus for received signal equalization

The modem of this invention overcomes problems associated with use in a wireless radio frequency communications channel. This modem provides a data carrier detection (DCD) function for associated data terminal equipment even though a transmission carrier or tone is not used. Provision is also made for communicating with data terminal equipment operating at a substantially lower data rate than the modem data rate without requiring a reduction in the modem data rate.

Modem suited for wireless communication channel use

A dental device for isolating a region of the mouth in which dental operations are to be performed includes a frame to retain the device in the mouth in substantially vertical orientation between the inside of the lower teeth and the patient's tongue. The frame includes a palatal member that engages the roof of the mouth and a lingual member connected to the palatal member to engage the mouth generally at the mouth floor. The palatal and lingual members are resiliently biased in a direction away from each other so that upon placement of the device in the mouth the device is in compressive engagement between the mouth floor and roof. The lingual member has a first portion disposed generally above the mandibular occlusal plane and extending outward to engage the lower teeth and a second portion extending generally downward below the mandibular occlusal plane. A shield member is affixed to the second portion and is sized to shield the tongue from the lower teeth. The tongue pressing against the shield member serves to stabilize the device in the mouth against lateral displacement with the second portion of the lingual member retained against the inside of the gums below the teeth.

Combined saliva ejector, tongue retractor and throat protector

An improved load cell scale which comprises a load supporting frame pivotally carried upon levers which bear upon a load cell on the frame and, are in turn, pivoted upon fulcrum pins. All pivot pins are journaled in oversized bores formed in the levers so as to rock the pins with a slight rolling motion in the bores under load-induced pivotal action, rather than with rotation about the pin axis.

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Huntsville, AL, United States of America

David Paul Nelson