Abstract: This invention provides for an off-the-record e-mail system that can ensure that messages, particularly sensitive messages, are available only for the intended recipient and never reside on permanent storage media. Control of the existence of the off-the-record e-mail can lie completely with the sender. The sender of the off-the-record e-mail sets the time-to-live (TTL) for the message content. When an off-the-record e-mail message is deleted, there is preferably no trace of the e-mail message on any computer backup system. The sender may also update the e-mail content at any time. The off-the-record e-mail system can include a personal server that combines the functions of a web server and an e-mail transfer server. The personal server may reside on an individual's personal workstation and might serve no one but that particular user. The personal server acts as a broker between the sender and the sender's SMTP server.

Abstract: Systems and methods for wireless communication are provided. In a particular embodiment, a base station device is disclosed that includes an interface coupled to a network to communicate with a central controller and a wireless transceiver adapted to communicate wirelessly with one or more portable devices via a local area network. The base station device also includes logic coupled to the interface and to the wireless transceiver. The logic communicates with the remote central controller device via the network to receive an authorization to communicate wirelessly. The logic selectively activates the wireless transceiver after receiving the authorization.

Abstract: A filter cleaning system according to one aspect of the invention comprises a baghouse including a tubesheet having a plurality of openings extending therethrough. A plurality of filter cartridges is sealingly mounted to the tubesheet at respective openings. Each filter cartridge has an open end and pleated media for filtering particulates from gas flowing therethrough. The filter cartridge has particulates accumulate on the pleated media. A pulse cleaning system intermittently directs cleaning pulses of air into the open ends of the filter cartridges media at a supply pressure in the range of about 20 PSI to 60 PSI to dislodge accumulated particulates from the pleated media.

Abstract: Systems and methods for wireless communication are provided. In a particular embodiment a base station device is disclosed that includes an interface coupled to a network to communicate with a central controller and a wireless transceiver adapted to communicate wirelessly with one or more portable devices via a local area network. The base station device also includes logic coupled to the interface and to the wireless transceiver. The logic communicates with the remote central controller device via the network to receive an authorization to communicate wirelessly. The logic selectively activates the wireless transceiver after receiving the authorization.

Abstract: A common password method is disclosed which provides both convenience and security assurance for users who have multiple accounts protected by passwords. According to the present invention, a user only needs to remember a common password to access any of the user's accounts. A designated password for each account is generated by a hash function of the common password and some account-dependent information. The hash value is calculated at the user's computer, and then submitted as a designated password to a server. Thus, each account is protected by the distinct designated password, and the common password is never revealed in an unauthorized manner.

Abstract: A method for providing a called party's telephone number in response to some online identifying information provided by a calling party. The calling party provides an entire or at least a portion of an electronic mail address, screen name or login name belonging to the called party. The electronic mail address, screen name or login name is associated with the called party's telephone number. The number is provided to the calling party and the calling party may be connected to the called party directly via the telephone network.

Abstract: The present invention relates to a multiple-user communication system wherein one carrier source is shared by a cascade of users of the system. More particularly, the present communication system uses a single carrier propagating along the system's transmissin medium onto which each user directly impresses the associated data or communication signal destined for another user preferably using either subcarrier angle modulation (phase or frequency) or TDM techniques for intensity or angle modulation. In the present system using subcarrier angle modulation, each user can either transmit or receive at a fixedly assigned or selectively assigned subcarrier channel, which is different from the subcarrier channel assigned to each of the other users. Where TDM techniques are used, the communication signal from a user can be directly impressed on the single carrier using intensity or phase modulation.

Abstract: Prior art circuits for recovering timing information from baseband digital signals include a rectifier and a separate phase detector for controlling the phase of a phase-locked voltage-controlled oscillator. In the circuit described herein, an antiparallel diode pair is used to perform the two functions of rectification and phase detection. The resulting timing circuit is, thereby, simplified. Alternatively, a dual-gate field effect transistor may be used.

Abstract: In stream cipher operation (FIG. 1), a public key cryptographic system employs a filter (21, 22, 31, 32, 33) to alter each sequence (S.sub.i) input to the encryption devices (FIGS. 2 and 3) at the transmitter and the receiver of the system. Characteristics of the filter are known only to the sender and authorized receivers.

Abstract: In a public key cryptographic system (FIG. 1) for communicating securely over an insecure communication channel (3), a sender (1, 2) enciphers a data message (D) using a public enciphering knapsack key (H) to generate an enciphered message (S.sub.H). An authorized receiver (4 6, 7, 20, 21, 22) with knowledge of a private deciphering key (E), a modulus (M) and an integer multiplier (W) generates a private enciphering key (A) which is employed in further enciphering the received enciphered message to form a doubly enciphered message (S.sub.E, S.sub.E). The doubly enciphered message is deciphered using the private deciphering key alone to recover the original data message.

Abstract: The present invention relates to a decoder for use in a spread spectrum radio receiver which is capable of directly demodulating an L-length frequency-hopped, Q-level frequency shift keyed radio-frequency received signal into a baseband signal wherein a desired user's message signal is decoded into a sequence of tone bursts at a fixed frequency over each L-length sequence. Spectral analysis is performed on the resultant baseband signal either during each chip interval or once at the end of each L-length sequence to permit subsequent detection of a desired user's correct received message signal.

Abstract: The present invention relates to a mobile radio base station (14) capable of communicating with a large number of mobile stations by implementing space diversity and time-division retransmission techniques in a digital communication system. The digital base station contains a plurality of antenna elements (16.sub.1 -16.sub.M) and a plurality of retransmission branches (18.sub.1 -18.sub.M) associated in a one-to-one relationship. When the base station receives a digital communication signal from a mobile station, each antenna element receives the signal with a unique random phase (.theta..sub.1 -.theta..sub.m) due to the effects of the environment on signal transmission. The signal is then processed through the plurality of retransmission branches, where each branch adapts to compensate for the random phase of the signal received by its associated antenna element.

Abstract: In a digital transmission system, disparity is defined as the difference between the number of binary digits at each code state. The generation of a block of binary digits having zero disparity possesses many advantages. The present invention discloses coding apparatus (100, 300) for converting a block of binary digits having random disparity into a zero disparity block, and vice versa. The coder accomplishes this translation by determining (103) the disparity of the random disparity block and then selecting (103, 104, 106, 107, 110, 111) a bit position which divides the block into two digit segments each having half this disparity. Inversion (115) of either digit segment generates a zero disparity block. For decoding, data representing the bit position selected is transmitted along with the zero disparity block. The binary digits previously inverted by the coder are then reinverted. This coding/decoding technique is adaptable to any block size having an even number of binary digits.

Abstract: The present invention relates to a wideband digital spectrometer capable of obtaining the Fourier power spectrum of a combination of an input signal, using the Walsh functions. The input signal is low-pass filtered (10) at a cutoff frequency f.sub.c, then sampled at a rate of 2f.sub.c (12) to provide N sequences representative of the digitized input signal. Each one of the N sequences is combined with a separate one of the N Walsh functions (14), and the Walsh power spectrum of each one of these N combinations is then computed (16). These N Walsh power spectrum components are applied to an N.times.N Walsh-Fourier power transformer (18) which generates the desired N Fourier power spectrum components.

Abstract: The present invention relates to a majority logic spread spectrum, FH-MFSK radio receiver capable of demodulating and decoding one or more concurrently received L-length frequency-hopping, 2.sup.K -ary frequency shift keyed signals to determine the correct signal of a particular user. In operation, the receiver spectrum-analyzes the received signal to determine which frequency components are present during each of the L chip intervals and then modulates a particular user's L-length FH address signal with the derived frequency components to arrive at a 2.sup.K by L-length detection matrix. A majority logic decision circuit determines the level having the maximum number of derived frequency components along the L-length axis of the matrix, or which is the most likely level of multiple equal levels, and decodes the chosen 2.sup.K level into the indicated message signal.

Abstract: The present invention relates to a precision phase modulator wherein a carrier signal of constant amplitude and frequency and a modulating signal are applied to the two inputs of the first one of a cascade of linear suppressed-carrier amplitude modulators. Each subsequent modulator of the cascade arrangement concurrently modulates the output signal of the previous modulator of the cascade with the modulation signal. The input carrier signal and the output signal of each modulator of the cascade is tapped-off and weighted, the weighted carrier input and outputs of the even-numbered modulators and the weighted outputs of the odd-numbered modulators are separately added and are combined in quadrature to provide a phase modulated output signal.

Abstract: The present linear amplifier uses nonlinear components where an input signal with amplitude and phase variations is concurrently applied to a limiter (41) and an envelope detector (42) which provide signals that serve as a carrier signal and a modulating signal, respectively, to a phase modulator comprising two or more linear suppressed-carrier amplitude modulators (50) connected in cascade. The weighted carrier signal and weighted outputs of the even-numbered amplitude modulators (50.sub.2, 50.sub.4, . . . ) are added separately from the weighted outputs of the odd-numbered amplitude modulators (50.sub.1, 50.sub.3, . . . ) to generate two signals which are combined in a quadrature coupler (56). The two outputs of the quadrature coupler are separately amplified in a pair of amplifiers (60, 61) and combined in a second quadrature coupler (64) to provide a substantially linearly amplified output signal of the input signal.