Abstract: The communication system comprises amplification units coupled to the radiating transmission line at periodic locations for amplifying communication signals radiating and traveling upstream and downstream on the transmission line. During normal operation, mobile communication units near the radiating transmission line can communicate with other mobile communication units near the transmission line as well as with a base station by transmitting communication signals at a first and second frequency. The amplification units also comprise degradation detection units which detect when the communication system has been degraded between any two amplification units. Upon detection of a degradation, the amplification units commence to amplify, transmit and receive the communication signals across the location of the detected degradation at a first fault frequency and a second fault frequency, rather than the first frequency and second frequency, respectively.

Abstract: A method for reliable communication within a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use by a subset of radio units by digital control signals transmitted over said control channel, said control channel carrying outbound digital control signals from a base site to said radio units, said outbound digital control signals having a fixed transmission time slot, said method comprising the steps of: (a) transmitting a first message and a second message, each 28 bits in length, within said time slot; (b) defining at least one first message type identifier field within said first message; (c) defining a group identifier in said first message, said group identifier comprising from greater than 11 up to 16 bits; (d) defining at least one second message type identifier field within said second message; (e) defining a logical identifier in said second message, said logical identifier comprising from greater

Abstract: A security system for a digital trunked radio system having a digital control channel and a plurality of working channels, wherein said working channels are assigned for temporary use of individual radio units by digital control signals transmitted over said control channel, said control channel carrying digital control signals between a base site and said radio units, comprising a digital key, said key used to limit access to the system equipment and system control channel transmissions.

Abstract: A method and system is disclosed that allows for the designation of over 1,000,000 individual users in a communication system, such as an EDACS system, using the existing five-digit portion of command message utilized for specifying the destination address. This is accomplished by using an Extended Addressing Digital Interface (EADI) protocol using hexadecimal characters in the command message rather than decimal characters, thereby creating an “extended addressing” (EA) capability. The largest five-digit hexadecimal number, FFFFF, corresponds to the decimal number 1,048,575, thereby realizing the ability to exceed one million users, without having to change the size (number of digits) in the command message. Backward compatibility is assured by adding new mode commands that identify a particular command message as being generated by EA compatible equipment.

Abstract: A radio frequency communication system utilizing a radiating transmission line for communicating data signals is disclosed. The data signals convey digital data to remotely located data devices, including computers, equipment control systems and digital video cameras. The data signals have a wide bandwidth of about 0.5 MHz to 32 MHz. In this way, the communication system creates a local area network by means of the radiating communication line. The communication system is intended to be used in environments where radio waves do not propagate well, such as in underground environments, and in particular mines. The communication system comprises at least one amplifier connected to the radiating transmission line for periodically amplifying the data signals by demodulating the data signals to recover the data contained therein and then modulating the recovered data into a regenerated radio frequency at a power level permitting transmission and radiation of the regenerated radio frequency data signal.

Abstract: Squelch circuit and method useful in frequency-scanned radio receivers are provided. Generally, the squelch circuit includes an audio-removal filter coupled to receive an audio signal. The passband of the audio-removal filter is selected sufficiently high relative to frequency components of the audio signal. An absolute value detector is coupled to the audio-removal filter to supply an output signal having a positive polarity regardless of the polarity of the signal supplied by the audio-removal filter. An integrating filter is coupled to receive the output signal from the absolute value detector and supply an integrated signal. The integrating filter has at least one selectable filter coefficient indicative of the response time of the integrating filter.

Abstract: Method and computer-readable medium are provided for controlling signaling and channel assignment in a decentralized trunked radio system to operationally mimic a centralized trunked radio system. The method allows monitoring a parameter indicative of elapsed time of channel activity, such as control channel or working channel activity or both, presently being carried in a respective one of a plurality of radio frequencies assigned to the radio system. Upon the parameter indicative of elapsed time of channel activity reaching a respective target value, the method allows determining whether there is another radio frequency in the plurality of radio frequencies assigned to the radio system available for carrying the channel activity presently being carried by the one radio frequency. If the determining action indicates the presence of an available radio frequency for carrying the channel activity, the channel activity is shifted from the one radio frequency to the available radio frequency.

Abstract: A proxy is utilized to limit the RF bandwidth needed for foreign IP registration. An existing RF log-in procedure causes the proxy to initiate and complete the foreign IP registration procedure with the foreign agent at the RF site where the mobile node is located. The proxy then acts as a locally connected (i.e., direct ethernet connected) device for each IP address for which it is proxying, and thus there is no need to use RF to register a mobile with the active foreign agent. This allows the use of off-the-shelf home and foreign agents to complete the mobile IP architecture, and reduces the RF bandwidth used, since the RF portion of the registration process (the registration between the active foreign agent and the mobile) is reduced.

Abstract: A synchronized communication system for communicating signals into and from a medium is disclosed. The communication system utilizes a transmitter located at a central station external to the medium, which transmits a low frequency synchronization signal into the medium. Transceivers located within the medium receive the low frequency synchronization signal and send information radio signals synchronized with the low frequency synchronization signal to a receiver located at the central station. Zone transceivers are located within the medium to receive and retransmit the synchronization signal at the low frequency within a zone. The zone transceivers also receive information signals from transceivers in the zone and transmit zone information radio signals to the central station containing information corresponding to the information received from the transceivers in the zone.

Abstract: Method processor and processor-readable medium for reducing the level of feedback-induced noise in the output signal from an audio automatic gain control circuit are provided. The method allows for receiving a stream of pulses comprising an input signal to the automatic gain control circuit. The method further allows for receiving estimates of respective high and low frequency energy components of the input signal. The respective high and low frequency components are averaged, e.g., over a respective sliding window. An energy scalar is calculated based on the ratio of a predefined target energy level over a combined value of the high and low frequency components. A relating action allows to compare the target energy level to the combined value of the high and low frequency components. Based on the comparison results, the calculated energy scalar is limited to within the two limit values.

Abstract: Method and processor for determining loading of a communications system shared by a plurality of user-terminals are provided. The method allows a respective terminal for monitoring a control channel including logical messages therein. The monitoring of the messages in the control channel is performed regardless of whether or not the logical messages therein are specifically addressed to that terminal. The method further allows for estimating a parameter indicative of system loading based on information in the monitored logical messages.

Abstract: Single Channel Autonomous Trunking (SCAT) radio frequency systems and methods use a single duplex Time Division Multiple Access (TDMA) channel for the control and working channels thereof. By providing a single duplex TDMA radio frequency channel including a plurality of TDMA time slots in SCAT systems and methods, the SCAT systems and methods can simultaneously operate in a control channel mode and a working channel mode using the single duplex TDMA radio frequency channel.

Abstract: An electrical connector for interconnecting a portable radio and accessory devices. The connector attached to the accessory device includes a slot for initially engaging a tab on the portable radio, which provides proper alignment between the portable radio and the connector, while the connector is rotated toward the portable radio. Maintaining alignment ensures proper mating between the electrical contacts of the portable radio and the electrical contacts of the connector, and further ensures that a quarter turn latching device of the connector is properly received by a receiving member on the portable radio. The user then rotates the quarter turn latching device to urge the contacts against each other and secure the connector in place. Because the electrical connector includes a two-point attachment mechanism to the portable radio, rotation of the connector relative to the portable radio is prevented.

Abstract: Calls are transferred from a first call to a second call in a trunked digital radio communications system that includes a first transmitting user terminal that communicates with a receiving user terminal or group of user terminals in the first call over a first working channel via a base station. A second call is transmitted from a second transmitting user terminal to the base station over a second working channel, that identifies the receiving terminal. Transfer data is transmitted from the base station to the receiving terminal or group of user terminals in the first call on the first working channel, the transfer data identifying the second call and the second working channel. The transfer data is detected in the first call on the first working channel at the receiving user terminal and the receiving user terminal transfers to the second call on the second working channel based upon the transfer data.

Abstract: A radio frequency communication system utilizing a radiating transmission line for simultaneously communicating audio and video signals is disclosed. The video signals convey video information and the audio signals convey narrow band computer data or audio information. The communication system also provides several separate channels allowing simultaneous audio communication between a plurality of mobile stations. The communication system is intended to be used in environments where radio waves do not propagate well, such as in underground mines. The communication system comprises at least one amplification unit connected to the radiating transmission line for periodically amplifying the audio and video signals. The amplification units have a separate amplifier for amplifying each of the signals and each amplifier is connected to the transmission line in parallel. The amplifiers utilize transistors operating in the linear region.

Abstract: A radio frequency communication system utilizing a radiating transmission line is disclosed. During normal operation, a mobile communication unit near the radiating transmission line can communicate with other mobile communication units near the transmission line as well as with the base station. The communication system is redundant in that if a portion of the communication system fails such that communication signals cannot be communicated through the fault the communication system will continue to operate and communication signals from any mobile communication units near the radiating transmission line will be transmitted and received from the base station. The communication system is particularly suited for use in underground mines in which event the base station can be located at the surface, and the mobile communication units are generally located in the mine shafts.

Abstract: A pet containment system uses a transmitter for transmitting a series of electromagnetic signals, and a receiver removably attached to the pet for receiving the series of electromagnetic signals from the transmitter. The transmitter includes means for modulating the electromagnetic signals, means for transmitting the resulting non-random patterns of electromagnetic energy, and at least one transmitting antenna. The receiver includes at least one receiving antenna, means for comparing the signal level of the received electromagnetic signals from said transmitter with a predetermined level and for producing an electronic indication of a loss of signal, means for comparing the phase of the received electromagnetic signals from said transmitter with a reference phase and for producing an electronic indication of a loss of phase, means for producing a warning stimulus to the pet, and means for producing a control stimulus to the pet.