Abstract: A highly fault tolerant method of radio communication of information in the form of a message packet employs a distributed network of transmitter/receivers `transceivers` each having a unique identification ("ID") number. An initiating transceiver creates a message packet having the ID of a transceiver intended to receive the message packet. It then broadcasts the message packet to transceivers within its transmission range. Each transceiver which receives the message packet checks to see if there are errors and sends an acknowledgement if no errors. The transceivers determine valid message packets by determining if the message has not expired, if it has not been seen before and there were no errors in the received message packet. The transceiver also determines if the transceiver ID in the message packet match its own transceiver ID, and if it does, is the message has been successfully transmitted to its intended transceiver.

Abstract: An alternating current sensor employing a mutually-inductive current sensing scheme comprises a conductive pipe and a cylindrical-shaped conductive element at least partially surrounded by the pipe. The pipe is substantially concentric to the conductive element and a conductor electrically connects a pair of corresponding ends of the pipe and conductive element to form a connected conductive path through the sensor. The conductive element may include a passage or opening shaped to form a magnetic field within the passage during current flow along the conductive path.

Abstract: Apparatus for detecting defective conditions associated with a set of railway vehicle wheels and with a railtrack upon which a given railway vehicle travels comprises a rotation measurement unit for generating data indicative of rotational rate of the set of wheels; a motion sensor, such as an accelerometer or vibration sensor, for generating data indicative of motion along a vertical axis relative to the railtrack; and a data processor coupled to the motion sensor and to the rotation measurement unit for receiving the rotational rate and motion data. The data processor is designed for detecting, based on the received rotational rate and motion data, a defective condition associated with the wheel set and for detecting, based on the received motion data, a defective condition associated with the railtrack. The apparatus can be operatively combined with a mobile tracking unit for a vehicle tracking system.

Abstract: An alternating current sensor employing a mutually-inductive current sensing scheme comprises a conductive pipe and a cylindrical-shaped conductive element at least partially surrounded by the pipe. The pipe is substantially concentric to the conductive element and a conductor electrically connects a pair of corresponding ends of the pipe and conductive element to form a connected conductive path through the sensor. The pipe and the conductive element are spaced apart a predetermined radial distance to form a magnetic field in the space between the pipe and conductive element during current flow along the conductive path.

Abstract: An optical communications system includes apparatus for interferometric signaling in which light signals are propagated from a first location so as to form at least one predetermined interference pattern at a second location remote from the first location and then the received light signals are demodulated at the second location. The apparatus includes a substantially coherent light source and a plurality of adjacent, substantially coplanar optical modulators in the path of the emitted light.

Abstract: A munitions cartridge transmitter capable of emitting an electromagnetic signal after discharge from a cartridge propelling device comprises a signal generator, an electromagnetic signal transmitter coupled to the generator, an antenna coupled to the transmitter, and a hollow cartridge for housing the generator, the transmitter, and the antenna. The transmitter is energized after discharge of the cartridge propelling device by a power source contained in the cartridge.

Abstract: In one embodiment, the present invention is an encryption/decryption and authentication algorithm. The algorithm has three major steps. The first step is generating cipher text. The second step is generating the authentication field. The third step is encrypting or deciphering the appropriate data in the message. One byte of cipher text is generated for every byte of plain text contained in the message. After all the cipher text is generated, a four byte authentication field is generated using the last four bytes of cipher text. The message is then scanned for data fields which have been encrypted or are to be encrypted and the corresponding byte of cipher text replaces the message bytes. The encryption is accomplished by sending the cipher text instead of message text. To decipher the message, the algorithm operates in a reverse mode to replace the cipher text with the message text, i.e., the algorithm is a self-reversing process.

Abstract: A public key cryptographic mechanism provides a measurable degree of minimum security, in an ensemble sense, for two Parties, A and B, to establish a commonly held private cryptographic keying variable between them for establishing communications. Both parties randomly generate m-bit vectors vec.sub.-- A and vec.sub.-- B, store the vectors, then copy the vectors and add m-bit vectors containing n ones. The vectors thus modified are exchanged between the parties. Both parties then respectively bit-by-bit combine, by Exclusive-Or logic, their stored m-bit vectors vec.sub.-- A and vec.sub.-- B with a received vector, denoted rec.sub.-- B and rec.sub.-- A, to generate respective vectors W.sub.-- A and W.sub.-- B. Parties A and B then generate all ##EQU1## vectors at a Hamming distance n from W.sub.-- A and W.sub.-- B respectively. These ##EQU2## vectors are each bit-by-bit added, using Exclusive-Or logic, with their encryptions under a publicly known keying variable K.sub.1, forming image vectors.

Abstract: A countermeasure to a partial-band follower jammer for frequency hopping spread spectrum communication systems employs an M-ary orthogonal frequency shift keyed (FSK) signaling system having q frequency channels available for hopping. During each signaling interval, the transmitter and receiver operate in either a conventional or unconventional mode. The conventional mode is selected by the transmitter and the receiver with a pseudorandom probability p.sub.c. In this mode, the transmitter transmits one of r tones within the corresponding hop (i.e., within one of q channels), and log.sub.2 r information bits are conveyed, while the receiver comprises a dehopper followed by noncoherent matched filters. The unconventional mode is selected with probability 1-p.sub.c. In this mode, the transmitter randomly chooses one of the r tones and transmits it in one of r channels within each hop, where the r channels are selected pseudorandomly. In the unconventional mode, log.sub.

Abstract: A method, apparatus and system are provided for recognizing broadcast segments, such as commercials, in real time by continuous pattern recognition without resorting to cues or codes in the broadcast signal. Each broadcast frame is parametized to yield a digital word and a signature is constructed for segments to be recognized by selecting, in accordance with a set of predefined rules, a number of words from among random locations throughout the segment and storing them along with offset information indicating their relative locations. As a broadcast signal is monitored, it is parametized in the same way and the library of signatures is compared against each digital word and words offset therefrom by the stored offset amounts. A data reduction technique minimizes the number of comparisons required while still maintaining a large database.