Motorola Corporation

Other

John Paul Byrns

Ezzat A Dabbish

Michael J McClaughry

Larry C Puhl

Stephen N Levine

Michael W Bright

Daniel P Brown

Eric F Ziolko

A method and apparatus for transmitting data improves efficiency and guarantees consistency in the data transmission rate. According to the method and apparatus, a data offset byte ( ) is determined for a frame of data to be transmitted. The data offset value is used to modify the data bytes of the data frame to insure that the modified data bytes does not include control bytes ( ) which are sent with the data. The offset value and the modified data bytes are then sent ( ) to a receiver which recovers ( ) the data. Accordingly, only one offset byte must be transmitted for each frame of data.

Method and apparatus for transmitting data

A cryptographic apparatus for encrypting and decrypting digital words includes a mechanism that permits a cipher algorithm to be electronically stored after the manufacture of the apparatus. The storing mechanism includes at least one electrically erasable, programmable gate array containing a portion of the cipher algorithm and at least one random access memory device coupled to the array for storing digital data generated by the algorithm. A mechanism which is coupled to the gate array and memory device controls the execution of the algorithm for each digital word thereby decrypting encrypted digital words and encrypting non-encrypted digital words.

Cryptographic method and apparatus with electronically redefinable

An improved semaphore is described that arbitrates the access of a memory shared by first and second microcomputers operating asynchronously at the same speed or at different speeds. The semaphore includes a semaphore flip-flop producing a binary semaphore signal indicating whether or not the semaphore is owned, and an ownership flip-flop producing a binary ownership signal indicating which of the first or second microcomputers previously owned the semaphore. First gating circuitry decodes control signals from the first microcomputer and generates a read or write pulse signal. The read pulse signal from the first gating circuitry loads the semaphore signal and ownership signal into first and second flip-flops, respectively, whose outputs are applied to the data bus of the first microcomputer. Second gating circuitry decodes control signals from the second microcomputer and generates a read or write pulse signal. The read pulse signal from the second gating circuitry loads the semaphore signal and ownership signal into third and fourth flip-flops, respectively, whose outputs are applied to the data bus of the second microcomputer. If the first and second microcomputers access the semaphore simultaneously, access is granted to the second microcomputer since the output of the third flip-flop resets the first flip-flop to deny access to the first microcomputer.

Semaphore for memory shared by two asynchronous microcomputers

A method for synchronizing the scrambling sequences of communicating scrambler units of a privacy communications system in a reliable and secure manner. The method is particularly adapted for use in noisy or fade prone transmission environments, and permits late entry of authorized third parties to the system. The method utilizes digital sequences interleaved periodically with scrambled analog information to provide reliable synchronization.

Scrambler key code synchronizer

A data transmission system is described where data signals are bidirectionally transmitted between a data transmitter and a plurality of data receivers in a self-clocking bit streams carried on true data and complement data signal lines and a non-return-to-zero (NRZ) bit streams on a return data signal line. According to an inventive data transmission scheme, data signals are transmitted by the data transmitter by utilizing the four possible two-bit binary states of the true data and complement data signal lines. Of the four two-bit binary states, a word state is provided before and after the data signal and a one state or zero state followed by a bit state is provided for each bit of the data signal. The data receivers detect the bit state to recover a bit clock signal and detect the one state and zero state to recover an NRZ data signal. In response to the bit clock signal, the NRZ data signal is serially shifted into a register while a previously parallel loaded return data signal is shifted out of the register and applied to the return data signal line. The inventive data transmission scheme is self-clocking and highly immune to speed and timing variations in the transmission. The inventive data transmission may be advantageously utilized for data transmission in many different data transmission systems, such as computer systems for data transmission between a microprocessor and peripheral units and control systems for data transmission between a central control station and geographically remote stations.

Self-clocking data transmission system

A demodulator is described for demodulating phase-encoded data signals transmitted on a noisy communication channel, such as, for example, radio communication channels of a radio communication system. The demodulator includes a digital phase-locked loop for phase-locking to the mid-bit transitions of the phase-encoded data signal, which, in the preferred embodiment is encoded according to the well known Manchester coding format, and further includes demodulating circuitry for sampling the phase-encoded data signal a predetermind number of times, weighting the samples according to predetermined weighting factors, totalizing the weighted samples for each bit interval and comparing the totalized samples to a predetermined threshold value for ascertaining the logical state of each bit of the phase-encoded data signal. For example, if the magnitude of the totalized samples is greater than or equal to the threshold value, a logical one state may be provided for the decoded data signal, and, if the magnitude of the totalized samples is less than the threshold value, a logical zero state may be provided for the decoded data signal. In preferred embodiments of the present invention, the weighting factors assigned to each sample may be either binary weighted or sine weighted, although any suitable weighting factors may be utilized depending on the characteristics of the phase-encoded data signal. The phase-encoded data signal demodulator embodying the present invention is particularly well adapted for demodulating high speed, phase-encoded data signals transmitted over radio channels to mobile and portable stations of a radio communication system.

Phase-encoded data signal demodulator

A bacteria filter has a base member with an open circular groove in which an adhesive bonding material anchors one end of a generally cylindrical filter element. The filter element has longitudinally extending pleats and the opposite end of the filter is adhesively secured in an open circular channel in an end cap element opposing the base member. A housing for the filter is sealed to the base member in spaced surrounding relationship with the filter element and has an inlet passage therethrough whereby air may enter the filter device through the inlet passage, flow through the filter element, and be emitted through the outlet passage in the base member. The method of assembling the filter device includes a unique method of retaining the pleated filter element in the desired cylindrical form while bonding the filter element to the base member and/or end cap.

Bacteria filter and method of assembling same

A bacteria filter includes a pair of generally conical housing sections having confronting marginal flanges adapted to be welded together to seal the sections into an integral filter housing. The flanges have a pair of tongue-in-groove connectors to facilitate alignment of the sections during assembly and to automatically stretch a filter element between the two sections during assembly to optimize the filtering capacity of the filter. Each section of the filter device has a co-axial tubular neck extension defining an inlet and outlet of the filter device.

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Hoffman Estates, IL, United States of America

John Paul Byrns