Abstract: A continuous speech recognition system employs a grammar tree of alternative potentially recognized word paths. A technique of tracing back through the grammar tree is utilized in determining which partial word path is common to all potential word paths. The common partial word path is deleted and words corresponding to the deleted partial word path are output as recognized words.

Abstract: A slotted CSMA contention technique and arrangement is disclosed for use in a radio data communications systems having a central base station/controller and a plurality of remote data terminals operating over inbound and outbound channels. The channels are divided into major frames, which are further divided into minor frames, which in turn are divided into microslots. An arrangement is devised whereby channel access may be prioritized as between periodic and aperiodic messages by advantageously utilizing the occurrence of these microslots so as to give priority to the former while completely eliminating collisions therebetween and, at the same time, optimally controlling the efficiency of the system as a whole.

Abstract: A method and apparatus are disclosed for improved channel selection in a multi-frequency radio data communications system whereby a minimum level of signal/service quality may be maintained at all times without unduly impacting channel loading considerations. Specialized idle messages are utilized in the outbound channel of the radio system which are required in any event but include added information for the monitoring remote terminals to determine channel quality and take appropriate action by selecting a new channel to operate on if channel quality falls below a preset threshold level.

Abstract: A paging system comprising a centrally located terminal and a plurality of remote pager units is disclosed wherein both automatic and manual acknowledge back signalling is provided. An appropriate acknowledge back signal by a called pager within a set interval indicates the message was duly receivied and understood which is so indicated to the initiating caller. Failure to respond within the set interval causes the pager unit to send back a negative response which is likewise so indicated to the initiating caller.

Abstract: A universal PSTN page entry protocol method and arrangement is disclosed whereby any type of incoming call may be accommodated at a single telephone input, be it a call from a standard telephone set or from a computer/VDT or PET terminal device. This permits an originating call to any type of pager whether tone-only, tone and voice, numeric and/or alphanumeric pagers.

Abstract: 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.

Abstract: The present invention describes a method and arrangement for reducing a sequence of initial frames into a reduced set of representative frames by combining the initial frames into a plurality of representative frames, the combining process including generating a distortion measure associated with each representative frame and comparing each distortion measure to a distortion threshold. From these representative frames, a set of mutually exclusive frames is determined to minimize the number of representative frames, whereby each representative frame in the set represents a unique set of contiguous initial frames and has an associated distortion measure which does not exceed the distortion threshold.

Abstract: A low impedance, spring loaded electric connector which comprises a cylindrical body receiving a conductive wire, a plunger guided by the body and having a tip for electrically contacting with an external conductive surface, a spring compressed between the body and the plunger. The plunger can slide along the body, and is biased by the spring to assure reliable contact with the conductive surface. This connector, further, includes a resilient and conducting cantilever making sliding contact between the plunger and the body for establishing an electric path bypassing the spring. The cantilever may be formed as a portion of the plunger, or alternatively may be made as a separate one attached to the plunger or the body.

Abstract: A communication system utilizing a plurality of receiving antenna which receive digital signals and process all of the received signals in the same trellis type decoder. Hamming weights are applied to each of the signals in accordance with the Viterbi algorithm with only the minimum Hamming weight for any one state transition path between any two levels in the trellis being retained. At the intersection of any two paths in the trellis, the path with the minimum Hamming weight is retained and the other path is discarded.

Abstract: Data is transmitted from a mobile or a base station to a booster or repeater station which, if it identifies that the same message has been retransmitted a preset number of times by the mobile or base station it automatically retransmits the data. The number of times a message has been retransmitted may be coded on each message or determined by comparing the retransmitted messages with a previously sent message that will have been stored in memory by the repeater and when the message in memory and retransmitted message are the same, registering another transmission of the message until the preset number is registered and then retransmitting the message preferrably from memory. In another arrangement the relay station receives and stores or otherwise identifies data from the mobile or base and listens for an acknowledgement from the receiving station, if no acknowledgement is received within a preset period of time the message is automatically retransmitted by the relay station.

Abstract: A user-interactive speech recognition control system is disclosed for recognizing a complete sequence of keywords (e.g., a telephone number such as 123-4567) via entering, verifying, and editing variable-length utterance strings (e.g., 1-2-3; 4-5; 6-7) separated by the user-defined placement of pauses. The device controller (120) utilizes timers (124) to monitor the pause time between partial-sequence digit strings recognized by the speech recognizer (110). When a string of digits is followed by a predetermined pause time interval, the recognized digits will be replied via the speech synthesizer (130). An additional string of digits can then be entered, and only the subsequent string will be replied after the next pause. Furthermore, the user has the flexibility to correct only the last digit string entered, or the entire sequence. Hence, if there is an error in only one digit, the erroneous digit string can be corrected without having to re-enter the entire digit sequence.

Abstract: A carry case for a portable hand held appliance such as a radio unit is disclosed which is constructed of a soft resilient shock absorbing material and includes a retainer bracket of semirigid material affixed to the interior back wall of the case. This bracket includes a self locating means for centering the portable appliance within the case and a latch means spring biased to locate and retain the portable appliance within the carry case. The radio may be removed by a user's hand contacting an upwardly extending flange to clear the latch means and permit the radio to be removed from the case.

Abstract: Method and apparatus are disclosed for printed circuit board assembly wherein optimal placement of components are effected. Components, such as microminiature components, are placed, at least on the underside of the circuit board, whereby specially contoured solder pads effect a self-alignment of such components prior to their being affixed in place by a suitable adhesive material.

Abstract: A radio communications system is described in which analog voice signals are transmitted and received via single sideband amplitude modulation, and digital data signals are transmitted and received via narrowband frequency modulation in a single trunked radio system having dedicated channel bandwidths. The base station continuously transmits the FM signalling information on a dedicated control channel. The remote station transceiver initially acquires lock to the data channel FM carrier, which is then demodulated to determine the frequency of an assigned voice channel. The remote station then acquires lock to the single sideband pilot carrier on the appropriate voice channel. The controller incorporates a memory state for holding AFC for the mobile transmit frequency. In the preferred embodiment, the data channel incorporates 2400 bps FSK-FM data in a 6.