Abstract: A two-way paging system includes one or more transmitters, a plurality of receivers, and at least one two-way personal paging unit or pager. The two-way pager receives pages from the transmitter, and sends response signals which are detected by the receivers. The response signals are in the form of digital packets, including forward error correction encoding and digital symbols that each consists of a predetermined number of bits. The receivers detecting the response signals decode the response packets to verify their accuracy and to identify the digital symbols. At the receivers, "accuracy indicators" can be associated with the detected symbols, providing an indication of the probability of accuracy. In one embodiment ("microdiversity receiver") two receiver components are provided at a single receiver site, with a separate antenna for each receiver component.

Abstract: A method of modifying reverse channel messages in a two-way paging system (101) to authenticate reverse channel messages is disclosed. The intended frequency of the reverse channel message is converted into a unique binary integer. The binary integer is used to modify a checksum (207) in the reverse channel message so that the checksum is now dependent upon not only the message (205) contents but also the intended frequency of the reverse channel message. When received by a paging receiver (109) of the paging system, an identical calculation takes place and if the modified checksum transmitted with the reverse channel corresponds with the calculated checksum, the message is authenticated. Otherwise, the reverse channel message is rejected.

Abstract: A modulator that modulates and encodes data using data symbols, interspersed with pilot symbols, for transmission to another modem, and a demodulator that decodes data symbols of a signal received from another modem. In the demodulator, a received signal is sampled at four times the symbol rate. The sampled signal is converted to quadrature signals and low-pass filtered to produce a complex baseband signal. Data symbols in the complex baseband signal are sampled in synchronization with the start of each symbol based on the pilot symbols that are interspersed in the signal. By processing the pilot symbols, full modem synchronization is maintained down to a very low signal-to-noise ratio, through noise bursts, or even when the data symbols representing data are replaced by predefined sequences of data symbols that convey the dots and dashes of Morse code identifying the station transmitting the modulated signal.

Abstract: A method and apparatus for filter enhancement in an electrical system (8) is provided. The electrical system (8) includes an input circuit (10) having a filter (14) and an output circuit (20) having a filter (24). An input conductive enclosure (12) and an output conductive enclosure (22) protect the electrical system (8) from field coupling between the input circuit (10) and the output circuit (20). A choke balun (26) is connected between the input circuit (10) and the output circuit (20) to also eliminate conductive coupling. The elimination of unwanted coupling enhances the performance of the electrical system (8) by achieving greater stopband attenuation.

Abstract: A method of validating communications between a transmitting component and a receiving component of a paging system is disclosed. The transmitting component prepares an application protocol data unit (APDU) for transmission by selecting predetermined portions of the APDU for hashing. A hash code is output by the hash method and included in the APDU. The receiving component retrieves the same predetermined portions of the APDU for hashing. The receiving component then compares the hash code in the APDU with the hash code the receiving component calculated. If there is a match, then the APDU is accepted as authentic. If there is not a match, then the APDU is rejected.

Abstract: A two-way paging system (10) includes a plurality of personal paging units (16). The personal paging units (16) receive pages (18), and generate radio signals (28) in response to the pages. The system includes a transmitter (12) for generating the pages, and a receiver (14). The receiver includes first and second receiving circuitry (30) and (34). The first receiving circuitry receives radio signals from the personal paging units. The second receiving circuitry receives radio signals from a source other than the personal paging units. The receiver further includes a data processor (32) electronically linked with the first and second receiving circuitry in the receiver. The data processor determines the time period during which radio signals are received from the personal paging units by the first receiving circuitry, based on radio signals received from the other source by the second receiving circuitry. In a preferred embodiment, the second receiving circuitry receives radio signals from the transmitter.

Abstract: A method for handling alarm conditions from paging stations in a paging system is disclosed. The paging system includes a paging terminal, a plurality of paging stations, and a network manager. When a paging station has an alarm condition, the paging station forwards the alarm to the network manager, which in turn, compares the alarm with an alarm record for that paging station and determines whether or not that alarm is a higher priority than the previous alarms received from the paging station. If so, the network manager transmits a signal to the paging terminal to page the technician responsible for servicing that particular paging station. The technician is paged and dispatched to the paging station for service.

Abstract: A method of transmitting paging messages over a paging system configurable to provide coverage over a primary geographic area or region and at least two subregions defined within the primary geographic region. The paging system consists of a plurality of paging transmitters that broadcast paging messages to the primary geographic region. Some of the plurality of paging transmitters are also assigned to broadcast to a particular subregion within the primary geographic area. During primary operation, for part of a predetermined period of time, all of the paging transmitters within the paging system simulcast paging messages to subscribers entitled to coverage over the whole primary geographic region. For a remaining period of broadcast time, each of the paging transmitters assigned to broadcast to a respective subregion broadcast paging messages intended for subscribers entitled only to paging coverage within that particular subregion.

Abstract: A linear transmitter (101) using predistortion includes a modulator (103), a predistorter (107), a digital quadrature modulator (111), an upconverter (113), a power amplifier (115), and an antenna (117). In addition, the transmitter (101) has a feedback loop including a coupler (119), a downconverter (123), a digital quadrature demodulator (125), and a trainer (131). The digital data to be transmitted is provided into the modulator (103), which converts the digital data into in-phase and quadrature component signals. The in-phase and quadrature component signals are then provided to the predistorter (107), which "predistorts" the component signals prior to amplification. The digital quadrature modulator (111) converts the component signals into a single analog signal. The upconverter (113) upconverts this signal from the predistorter (107) into the desired frequency of transmission, which is provided to the power amplifier (115) and the antenna (117) for amplification and broadcast.

Abstract: An hierarchical addressing mechanism for use in a paging system is disclosed. The paging system assigns a compressed organization identifier to each of the organization identifiers for the organizations that are sharing the resources of the paging system. Each of the pagers within the paging system are provided with an associative table that associates the compressed organization identifiers with organization identifiers. In operation, the paging system forms a page by appending an address word to a message. The address word includes the compressed organization identifier determined from the associative table and the pager identifier for the called pager. In this manner, a more efficient method of addressing pagers is disclosed.

Abstract: A satellite receiver includes a signal acquisition unit that is operative to receive a validation signal from a station controller located at a paging station. The satellite receiver is operative to lock onto a satellite signal. When the satellite receiver locks onto a satellite signal, the satellite receiver demodulates the satellite signal into a digital data stream that is forwarded to the station controller for packaging and retransmission as a page. The station controller includes circuitry to determine if the digital data stream is correct and intended for the station controller. If the digital data stream is correct, the station controller generates a validation signal and forwards the validation signal to the signal acquisition unit of the satellite receiver. If the digital data stream is incorrect, the station controller will forward a negative validation signal to the signal acquisition unit.

Abstract: A clock synchronization system for synchronizing a number of paging stations (24) with a system controller (23). Each paging station has a clock that includes a counter (52) that indicates the current local time and which is sequentially incremented by a counter advance signal applied thereto. A voltage controlled oscillator (58) generates the clocking signal that controls the advancement of the counter. A CPU (50) in the system controller monitors the time indicated by the counter and compares it to timing information received from a system clock. The timing information includes a time mark and a time mark send time. The system clock transmits to each paging system the time mark. At a future time, the system clock transmits the time mark send time which is the precise time at which the time mark was transmitted. The paging stations each measure the time interval between the time at which the time mark arrived and the time at which the time mark was transmitted by the system clock period.

Abstract: An input radio frequency signal to be amplified is fed to the gate terminals of parallel field effect power transistors through impedance matching networks that comprise parallel resistor-capacitor combinations. The capacitor is selected so that it is self-resonant at the frequency of operation, thereby preventing attenuation of the input signal at that frequency. A shunt resistor is coupled between the gates of the parallel transistors to eliminate odd mode oscillations.

Abstract: A modulator that modulates and encodes data using data symbols, interspersed with pilot symbols, for transmission to another modem, and a demodulator that decodes data symbols of a signal received from another modem. In the demodulator, a received signal is sampled at four times the symbol rate. The sampled signal is converted to quadrature signals and low-pass filtered to produce a complex baseband signal. Data symbols in the complex baseband signal are sampled in synchronization with the start of each symbol based on the pilot symbols that are interspersed in the signal. By processing the pilot symbols, full modem synchronization is maintained down to a very low signal-to-noise ratio, through noise bursts, or even when the data symbols representing data are replaced by predefined sequences of data symbols that convey the dots and dashes of Morse code identifying the station transmitting the modulated signal.

Abstract: A two-way paging system includes a paging terminal and one or more transmitters and receivers. The paging terminal, transmitter and receiver are synchronized to a common clock reference which is derived from the global positioning satellite system. The transmitter transmits paging signals in sequential frames having a predefined start time and duration. A paging unit is instructed to transmit its acknowledge signal during a predefined time slot. By synchronizing the paging terminal transmitters and receivers to a common clock the receivers are able to determine the frame number and time slot during which an acknowledge signal is transmitted based on the time of reception of the acknowledge signal. If the acknowledge signal is transmitted during the correct flame and time slot, the paging system can determine that the paging unit has received the paging message correctly.

Abstract: An improved architecture for providing high capacity capability to voice message systems is disclosed. The system includes a plurality of stand-alone voice message processors (VMP), each of which are communicatively connected via a high-speed local area network. Each of the voice message processors are communicatively connected to a network interface module (NIM) that receives all incoming calls from a public switched telephone network (PSTN). A control module is connected to the NIM and also interfaces with each of the VMPs over the local area network. As each incoming call is received, the control module routes the call to the appropriate VMP assigned to the subscriber to whom the call is designated. A terminal server is also connected to the local area network. The terminal server receives calls from subscribers utilizing a personal computer. In this manner, a subscriber can access his or her voice mailbox account.

Abstract: An integrated chassis slide assembly (10) is provided for integration with a chassis (12) and coupling to a mounting rack (not shown). The integrated chassis slide assembly (10) includes a fixed slide (14) coupled to the mounting rack (not shown), at least one intermediate slide (16), and an integrated chassis slide (18), where the integrated chassis slide is attached to the chassis (12) and forms a side panel of the chassis. The top and bottom edges of both the intermediate slide (16) and the integrated chassis slide (18) are bent over and outward to form opposed U-shaped channels (86, 106), and all the slides are slidably interlocked in a nested fashion, with the top and bottom edges of the fixed slide (14) nested within the channels (86) of the intermediate slide (16), and the channels of the intermediate slide nested within the channels (106) of the integrated chassis slide (18). Such interconnection allows for easy extension and retraction of the chassis along the assembly slides.

Abstract: A telecommunications system that performs page-connect paging is disclosed. The telecommunications system of this invention includes a paging system (28) that is designed to receive calls from page-connect paging system subscribers. Once such a call is received, the system (28) parks the call on hold while sending a page to the subscriber. The subscriber can then call the paging terminal (28) to automatically be connected with the calling party. The system further includes a cordless telephone-2 system (26) wherein each of the system subscribers is further provided with a portable handset (26) from which he can access the publicly switched telephone network. Subscribers with the handset, upon receiving a page-connect page, can automatically dial the paging terminal (28) to be connected to their calling parties.

Abstract: In a simulcast communication system, a method and apparatus for compensating differences in propagation time, lack of synchronization in transmitters, and multipath fading to recover data transmitted to a receiving device. In a simulcast communication system(26) that comprises a plurality of transmitters (32), a receiver (36) includes a digital signal processor (DSP) (86) that processes a demodulated received signal to adaptively compensate for changes in the channel through which a multipath signal is propagated from the transmitters to the receiver. In one embodiment, the DSP comprises a decision feedback equalizer. An error signal is produced by the equalizer through a comparison of the estimated symbols with symbols most likely transmitted, for use in updating filter coefficients used by the equalizer in processing the received signal. Alternatively, in a linear adaptive equalizer, reference or pilot symbols transmitted with the data symbols are used to determine the error signal.

Abstract: A time-division multiplexed paging system for transmitting multiple paging messages on the same frequency. A geographic area is divided into a plurality of cells having base stations that transmit radio frequency signals in the cells. Each base station is assigned a time slot at which paging messages may be transmitted. The assignment is made such that no base stations having overlapping radio frequency coverage areas transmit during the same time. A locate signal is simultaneously broadcast throughout a geographic area in order to locate a paging unit. Upon receipt of the locate signal, the paging unit transmits an acknowledge signal back to the paging system. The cell in which the paging unit is located is determined based upon the signal strength of the received acknowledged signal. A paging message is transmitted from the base station in the cell in which the paging unit is located during the time slot that is assigned to the base station.