Mine Communications and Tracking Glossary

Keywords: Communications Personnel tracking

A |B |C |D |E |F |G |H |I |J |K |L |M |N |O |P |Q |R |S |T |U |V |W |X |Y |Z

A

Access (network): Networks can be considered to have two responsibilities; one is to provide access and the other is to provide transport for data or voice.
Access link: In a node-based system, the first link, which is from the miner's handheld radio to a node, is through the air and is called the access link.
Access node: The node providing the service to the miner.
Access point (AP): A specially configured transmitting and receiving node on wireless local area networks (WLANs).
Accuracy: The measure of error in the miner's reported location.
Active tag: A tag that contains its own source of power for transmitting identification information.
Ad hoc network: A wireless ad hoc network is a decentralized wireless network. The network is ad hoc because each node is willing to forward data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity.
Air interface: See Access Link.
Allowable path loss: Allowable reduction in power density (attenuation) of an electromagnetic (EM) wave as it propagates through space.
Alternate communications path (ACP): A communications path that may be used to continue communications in the event that a primary path is blocked. A communications cable routed through a borehole is an alternate communications path.
Amplitude: For an electromagnetic or radio wave, amplitude refers to the maximum value of the periodically varying wave.
Analog signal: A signal whose amplitude varies continuously in time. See Digital Signal.
Antenna (stope): An antenna attached at the end of a leaky feeder cable, sometimes called a termination antenna, which is used to extend the range of radio coverage.
Antenna (termination): An antenna attached at the end of a leaky feeder cable, sometimes called a stope antenna, which is used to extend the range of radio coverage.
Arterial cable: The main or primary leaky feeder cable. It is typically installed in the track or main haulage entry of the mine.
Atmospheric monitoring system (AMS): This system is designed to detect potentially hazardous gasses in underground coal mines, It automatically provides visual and audible signals at all affected working sections and at all affected areas where mechanized mining equipment is being installed or removed when the carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in 30 CFR section 75.351. These signals must be of sufficient magnitude to be seen or heard by miners working at these locations. Methane signals must be distinguishable from other signals.
Attenuation: The reduction of a signal's amplitude or power.
Automatic gain control (AGC): An adaptive system in which the average output signal is fed back to the system to adjust the gain to an appropriate level for a range of signal input levels.
Auxilary antenna: A secondary antenna that can be used to help provide improved signal reception.
Availability: The probability that a system is operating properly when it is needed (i.e., the probability that the system has not failed or is not undergoing repair when it needs to be used).

B

Backbone system: A system that ties together several diverse systems and provides a common path for the transfer of communications or data. A leaky feeder is a common type of backbone system.
Backhaul: The communications path from an access node to the surface i.e., the mine operations center (MOC).
Backhaul link: The connection between nodes.
Backhaul system: A system that ties together several diverse systems and provides a common path for the transfer of communications or data. A leaky feeder is a common type of backhaul system.
Backup system: A system that may be deployed in the event that a primary system fails. For example, a medium Frequency system may be used as a backup in the event of leaky feeder failure.
Band: A specific range of frequencies in the electromagnetic spectrum.
Base station: A wireless communications station installed at a fixed surface location, i.e., the mine operations center (MOC). It is used to communicate with or to maintain contact with underground handheld or mobile radios and to activate one-way paging receivers.
Bi-directional: A communications system that passes information in both directions along its connected paths.
Bit: A binary digit equal to either a 0 or 1.
Bit error rate (BER): The number of bit errors divided by the total number of transferred bits during a studied time interval.
Brass in - brass out: Miners must check in before entering a mine and must check out once they have left the mine. In the past miners each had their own identification tags made of brass which were hung on a sign-in sign-out board. Now most miners are being electronically tracked using RFID tags.
Bridge: A device that provides interoperability between different technologies.
Bridge node: A node within a communications system that also acts as a bridge. See Bridge.
Bridge repeater: A repeater within a communications system that also acts as a bridge. See Bridge.
Byte: A byte is an ordered collection of bits (0's and 1's). Although there is no standard, typically there are 8 bits per byte. See Bit.

C

Capacity (communications system): The information carrying ability of a communications system.
Capacity (tracking system): The maximum number of people a tracking system can monitor in its coverage area.
Carrier frequency: The nominal frequency of a radio transmission. See Frequency.
Channel: A physical transmission medium such as a wire, or to a logical connecction over a multiplexed medium such as a radio channel. A channel is used to convey an information signal, e.g., a digital data from one or several transmitter to one or more receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.
Channel capacity: The upper bound on the amount of information that can be reliably transmitted over a communications channel.
Channel capacity: The upper bound on the amount of information that can be reliably transmitted over a communications channel.
Codec: The word codec stands for 'compressor-decompressor' or, more commonly, 'coder-decoder'. Codecs are used to convert an analog voice signal to digitally encoded version. A codec is a device or computer program capable of encoding and decoding an analog or digital signal.
Common backhaul device (CBD): A type of alternative wireless route when the normal route is unavailable.
Communications backhaul system (CBS): The portion of the communication system that comprises the intermediate links between the core network or backbone of the network and the nodes at the edge of the network.
Communications channel: A physical transmission medium such as a wire or to a logical connection over a muliplexed medium such as a radio channel.. A channel conveys information from a sender (transmitter) to one or more receivers. It has a certain capacity for transmitting information, usually measured by its bandwidth in Hz or its data rate in bits per second.
Communications link: A channel that connects two or more communicating devices. This link may be an actual physical link or it may be a logical link that uses one or more actual physical links.
Compressed voice: Audio (voice) that has been encoded so as to reduce the number of bits required for storage or transmission.
Constrained mesh network: A network where the allowable backhaul links that form the network topology must be pre-programmed into each node.
Coverage: Refers to the region or area in which radio-based communications services are available.
Coverage antenna: An antenna attached to a branch of a leaky feeder cable to provide coverage in a crosscut or portion of a parallel entry that does not have any leaky feeder cable in it..
Coverage area: The area within which radio communication is possible.
Coverage range: Maximum distance between the transmitter and receiver while still maintaining good quality communications.
Coverage redundancy: This refers to overlapping coverage sections, i.e., if one component or portion of a system becomes nonfunctional, that area will still be covered by another component or portion of the system. Redundant coverage ensures that the basic network remains in service. Redundancy allows for switching all communications to a secondary node or device when failure of the primary link occurs., The redundant link is able to fully replace the primary link in terms of speed and bandwidth so as to minimize the impact of a failed communication device.
Cross-band repeater: A device that effectively translates back and forth between two different frequency channels.

D

Dead reckoning: The process of predicting and fixing position by course, speed, and distance traveled.
Decibel (dB): A dimensionless logarithmic unit used for quantifying the ratio of a physical quantity (usually power or intensity) relative to a specified reference level between two values such as signal-to-noise ratio. A change in power ratio by a factor of 10 is a 10 dB change. A change in power ratio by a factor to tow is approximately a 3 dB change.
Decibel (dBc): Decibels relative to the carrier signal of the transmitting device.
Decibel (dBi): Used to define the gain of an antenna system relative to an isotropic radiator at radio frequencies. An abbreviation for "decibels relative to isotropic"�.
Decibel (dBm): The power ratio in dB of the measured power referenced to one milliwatt (mW). Zero dBm equals one milliwatt. A 3 dB increase represents roughly doubling the power (3 dBm = 2 mW)
Decibel (dBW): The power ratio in dB of the measured power referenced to one watt (W).
Demodulator: An electronic circuit (or software program in a software defined radio) that is used to extract or recover the information content from the modulated carrier wave.
Digital router: A networking device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers.
Digital signal: A signal in which the intensity maintains a constant amplitude for some period of time and then abruptly changes to another constant level where the different levels represent the binary digits 0 or 1. See Analog signal.
Digital subscriber line (DSL): A generic name for digital lines that are provided by telephone companies to their local subscribers and that carry data at high speeds.
Directional antenna: An antenna that focuses the energy in one direction.
Discrete antenna: An localized arrangement of conductors to radiate or receive electromagnetic waves such as a whip or dipole.
Distributed antenna: A dispersed antenna such as a leaky feeder cable when used in connection to a coal mine communications system.
Downlink: Pertaining to the transmission path from the base station to a mobile station.
Downstream: Downstream communications travels from the mine operations center (MOC) to the miner's communication device. Conversely upstream communications is sent from the miner's radio or phone to the MOC.
Dual independent communications path: Communications paths to the surface that do not depend on or transgress a common set of entries. Generally this means that the two paths out of the mine differ in direction from the mine by at least 90 degrees.

E

Electro-explosive device (EED): Aa general term for an explosive or pyrotechnic device such as a blasting cap that is initiated (detonated) by electrical energy.
Electromagnetic compatibility (EMC): The condition which prevails when electronic/electrical systems or equipment are performing their individually designed functions without causing/suffering unacceptable EMI degradation to/from other equipment in the same environment.
Electromagnetic energy: The energy carried by an electromagnetic wave.
Electromagnetic environment (EME): The radiated or conducted EM emission levels, in various frequency ranges that may be encountered by a system when performing its designed functions.
Electromagnetic interference (EMI): Electromagnetic energy which causes a malfunction in an electronic/electrical system or equipment, or interferes with its reception or processing of a desired signal. EMI may result from intentional and proper operation of equipment, or it may be unintentionally generated. EMI can be categorized as mild, medium, or severe, depending on the reaction of the victim equipment.
Electromagnetic radiation: A combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave effectively transporting energy and momentum. This can be in the form of radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays.
Electromagnetic spectrum (EM): A range of electromagnetic radiation frequencies. The term is normally used when referring to the frequencies as a group.
Electromagnetic wave: A form of radiated energy that travels in waves that are a combination of electric and magnetic fields.
Encoder-decoder (codec): The word codec stands for 'compressor-decompressor' or, more commonly, 'coder-decoder'. Codecs are used to convert an analog voice signal to digitally encoded version. A codec is a device or computer program capable of encoding and decoding an analog or digital signal.
Ethernet: A system or network for connecting a number of computer systems to form a local area network, with protocols to control the passing of information and to avoid simultaneous transmission by two or more systems.
Ethernet protocol: An Ethernet protocol is a system of digital message formats and rules for exchanging those messages in or between computer systems and in wireless communication. A protocol may have a formal description. Protocols may include signaling, authentication, and error detection and correction capabilities. A protocol definition defines the syntax, semantics, and, and synchronization of communication; the specified behavior is typically independent of how it is to be implemented. A protocol can be implemented as hardware or software or both.
Explosion-proof enclosure: an enclosure that is considered to be explosion-proof must meet three criteria. First, it must be an enclosure that is rugged in construction and suitable for use in mining applications; second, the enclosure has a minimum structural yield pressure of at least 150 psig, without significant permanent distortion; third, there shall be no visible luminous flames or ignitions of a combustible methane-air atmosphere surrounding the enclosure during explosion testing.

F

Fade margin: The difference between the received signal strength and the radio receiver sensitivity.
Fiber-optic backhaul: Fiber-optic is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. Fiber-optic backhaul is preferable to all other backhaul methods. Fiber links offer higher throughput speeds than any competing access technology and extremely high availability.
Frequency: For an electromagnetic or radio wave, frequency refers to the number of oscillations per second, measured in Hertz. See Hertz.
Full mesh: A mesh arrangement in which every node is connected to every other node.
Fully wireless: See Through-the-Earth System, TTE.

G

Gateway node: Provides the communications link to the surface facilities and supplies message routing information and other data to the access node.

H

Half duplex: A half-duplex system provides communication in both directions, but only one direction at a time (not simultaneously).
Handoff: Handoff is the process of changing the channel (frequency, time slot, spreading code, or combination of them) associated with the current connection while a call is in progress.
Hard-wired system: A communications system requiring physical wired connections between devices to operate.
Hardened system: A system in which protective measures have been taken to ensure the system's survivability. An example is enclosing a leaky feeder cable in a PVC pipe and burying it in a trench to enhance protection against roof falls.
Hardening: Increasing strength and ruggedness of system components to provide protection from damage.
Hardwired: Connected by physical wiring or cabling.
Head end: The main part of a leaky feeder system. It typically contains the voice and data radio repeaters, telephone interface, power supply, and stand-by batteries which are mounted in a standard 19â€� rack cabinet. The head end supports up to four leaky feeder output ports for redundancy.
Helical antenna: An antenna consisting of a conducting wire wound in the form of a helix.. In most cases, helical antennas are mounted over a ground plane. The feed line is connected between the bottom of the helix and the ground plane. Helical antennas can operate in one of two principal modes: normal mode or axial mode.
Hertz (Hz): A unit of measure equivalent to cycles per second.
Hop: An intermediate network connection consisting of a leg from one router to another router over which a packet travels to reach its destination.

I

IEEE 802.11: IEEE 802.11b/g is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands.
Immunity aspect: Refers to the correct operation of electronic equipment, referred to as the victim, in the presence of unplanned electromagnetic disturbances. Also referred to as susceptibility aspect.
Impedence: An electrical measure of opposition to alternating current (AC). It is defined as the frequency domain ratio of the voltage to the current and it has both a magnitude and a phase. If the circuit only has direct current (DC), then there is no distinction between impedance and resistance, as resistance is impedance with a zero phase angle.
Inby: Pertaining to the direction towards the coal face.
Inertial guidance: A navigation aid that uses a computer and motion sensors (accelerometers and gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity of a moving object without the need for external references.
Inertial navigation: A navigation aid that uses a computer and motion sensors (accelerometers and gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity of a moving object without the need for external references. See Dead Reckoning.
Inertial tracking: A tracking system that uses inertial navigation.
Infrastructure: All fixed location equipment within the mine and in entries to the mine.
Integrated system: A single system that provides both communications and tracking.
Interference: Stray electromagnetic energy (radiated, coupled, conducted, or induced) that causes undesirable or unacceptable responses, interruptions, malfunctions, or degradation of performance in a subsystem or equipment.
Intermodulation interference: EMI caused by the mixing, in a nonlinear junction, of two or more signals. The mixing process creates new signals at frequencies that are sums and differences of integral multiples of the original signals.
Internet Protocol (IP): A particular prescription or method used for communicating data across a packet-switched network.
Internet Protocol (IP) address: An Internet Protocol (IP) address is a numerical identification (logical address) that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes. Although IP addresses are stored as binary numbers, they are usually displayed in human-readable notations, such as 208.77.188.166.
Interoperability: The ability of different communications systems to communicate with one another.
Interrogate: Refers to the initial RF signal transmitted by an RFID tag reader to a tag, which begins the transfer of information between the two devices.
Intrinsically safe: Describes electrical equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal operations to cause ignition of an atmospheric mixture of methane in its most easily ignited concentration.

L

Latency: The time delay suffered by packets of information as they hop from node to node in a mesh network. More generally, the time it takes information to travel from one point to another in a communications network.
Leaky feeder: A communications device also known as "leaky coax," which assists wireless transmission. A coaxial cable that has been modified to allow signals traveling within it to leak out over its entire length.
Line amplifier: An amplifier for audio or video signals that feeds a transmission line; also called program amplifier
Line-of-sight (LOS): An unobstructed straight-line path between a transmitter and receiver.
Link budget: The quantitative result of an evaluation of the factors that contribute to RF power gain or loss in establishing a communications link between two components.
Link budget analysis: A link budget is the accounting of all of the gains and losses from the transmitter, through the medium (free space, cable, waveguide, fiber, etc.) to the receiver in a wireless communication system. It accounts for the attenuation of the transmitted signal due to propagation, as well as the antenna gains, cables, and other miscellaneous losses. Randomly varying channel gains such as fading are taken into account by adding some margin depending on the anticipated severity of its effects.
Local area network (LAN): A data communications system that lies within a limited spatial area, has a specific user group, has a specific topology, and is not a public switched telecommunications network, but may be connected to one.

M

MAC (Media Access Control) address: In computer networking, a Media Access Control address (MAC address) is a quasi-unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification.
Mean time between failure (MTBF): In computer networking, a Media Access Control address (MAC address) is a quasi-unique identifier assigned to most network adapters or network interface cards (NICs) by the manufacturer for identification.
Mean time to repair (MTTR): The average frequency with which a product fails or the average time between failure or the length of time a component or computer hardware is expected to work without failure. It is also an indicator of system reliability that is calculated from known failure rates of various system components. MTBF is usually given in units of hours.
Mediation device: A mediation device is a network component in a telecommunications network that receives, processes, reformats and sends information to other formats between network elements.
Medium frequency (MF) System: Communications systems that operate in the range of 300-3000 KHz. MF systems have been shown to work well in tunnels where there are metallic structures such as power lines and pipes. The signals can couple onto conductors and travel long distances.
Mesh network: A communications system where every node is connected to every other node and consequently has built in redundancy. In underground mines, this connectivity may be limited by the mine's geometry and cost considerations.
Mesh or node-based system: A communications system which relies on multiple individual devices to establish a communications path.
Mesh point: Another term for node in a node-based communications network.
Metric: A system or standard of measurement. Any type of measurement used to gauge some quantifiable component of performance.
Mine operations center (MOC): A command center which provides the real-time visibility and management of an entire service operation. The MOC must be operated twenty-four hours a day, seven days a week by emergency service personnel employed by the mine operator to provide emergency assistance and coordination to mine and industrial accidents or emergencies.
Mobile device: A pocket-sized computing device, typically having a display screen with touch input and/or a miniature keyboard (also known as a hand-held device, hand-held computer or simply hand-held).
Modulation: Modulation is the addition of information (or the signal) to an electronic or optical signal carrier. All modulation techniques involve operation on one or more of the three fundamental frequency domain parameters: amplitude, frequency, and phase.
Modulator: A device by which analog or digital information is converted to signals at RF frequencies suitable for transmission.

N

Network: A system containing any combination of interconnected communications equipment used to transmit or receive information.
Node: A point of connection into a communications network.
Node-based system: A node is a network junction or connection point. Every terminal,, computer, mobile device is a node.
Node-based tracking: An electronic tracking system using node-based communications nodes to determine radio location.
Noise: A received signal consists of the transmitted signal plus additional undesirable voltage or current distortions, usually considered random, which tend to obscure the transmitted signal. All noise is interference, but not all interference is considered noise.
Noise figure (NF): The ratio of actual output noise to that which would remain if the device itself did not introduce noise. NF is a number by which the performance of a radio receiver can be specified.
Non-directional antenna: An antenna that radiates energy more or less uniformly in all directions. Sometimes called an Omnidirectional Antenna.

O

Outby: Pertaining to the direction away from the coal face.

P

Parasitically couple: Medium frequency (MF) radio waves attach themselves (parasitically couple) to nearby existing metallic conductors within the mine entry.
Partial mesh: A mesh arrangement in which every node is connected to multiple other nodes.
Passive tag: A tag that does not contain its own source of power (battery).
Peer-to-peer communications: A communications system in which every handset can communicate with every other handset without the aid of the infrastructure in the mine.
Performance metrics: Measures of performance based on system behavior over a given period. These measures can be either qualitative or quantitative, e.g., bit error rates (BERs), received signal strength indications (RSSI).
Permissible: Refers to electrically operated equipment designed, constructed, and installed to ensure that such equipment will not cause a mine explosion or mine fire and, to the greatest extent possible, other accidents when used inby the last open crosscut of an entry.
Physical communications link: The path connecting one transmitter and one receiver through the interconnecting transmission media.
Point of presence: An artificial demarcation point or interface point between communications entities.
Point-to-Point (P2P): This is a full-duplex communications protocol using a serial interface that can be used on various physical media, including twisted pair or fiber optic lines.
Power barrier: Isolates the DC ground between the base and tunnel ends of the leaky feeder system, thereby eliminating ground gradients between two separately powered sections.
Power cell: A building block for a leaky feeder system made up of a power supply, amplifiers, and sections of leaky feeder cable.
Primary communications system: A communications system characterized by a transceiver small enough to be comfortably worn (carried) by a miner throughout an entire shift. Primary communications systems typically function at conventional radio communications frequencies, use small antennas, have a long battery life, and provide sufficient radio channels for general operations.
Propagation: The process whereby an EM wave travels through a surrounding medium, losing energy as it travels.
Propagation loss: The attenuation of signals passing between two points of a transmission.
Propagation ray path: The path that an electromagnetic (EM) wave takes as it propagates through a surrounding medium.
Protocol: The set of standard rules for data representation, signaling, authentication, and error detection required to send information over a communications channel.

R

Radio: A device used by individuals for voice or text communications.
Radio frequency (RF): The range of frequencies within which radio waves are typically transmitted, roughly 3 kHz to about 300 GHz.
Radio frequency identification (RFID): A system that uses radio waves to communicate identification information between a tag and a reader. In an underground mine electronic tracking system, the tag is worn by the miner and readers are placed throughout the mine.
Radio frequency interference (RFI): An unwanted disturbance that affects an electrical circuit due to electromagnetic radiation emitted from an external source. See also the definition for EMI.
Radio repeater: A combination of a radio receiver and a radio transmitter that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation.
Range: Limitation established by the separation distance due to energy being lost within the transmission media.
Reader: An electronic tracking system component that interrogates a tag.
Reader-based tracking: Reader-based systems are usually based on radio frequency identification (RFID) technology. An RFID tag is a small device (typically about the size of a postage stamp) which acts as a very small radio, able to transmit and receive messages. An RFID reader is a transmitter/receiver that reads the contents of RFID tags in the vicinity.
Received signal strength indicator (RSSI): RSSI is a technique in which the strength of the RF signal received is used to determine the distance of the transmitter from the receiver.
Receiver: An electrical device designed to receive electromagnetic energy.
Reconfiguration: The ability to create redundant routes in a network by adding nodes or changing to a different communications technology.
Redundancy: Redundancy involves the duplication of system functions to ensure that those functions will survive some level of damage to the system; in the context of communications systems, it is used to describe a system that can maintain communications with the surface when a single communication path is disrupted.
Redundant path: A redundant (secondary) path other than the normal (primary) operations path. It is designed to provide communications with the surface when the normal operations path is disrupted. The redundant system must be installed in a separate entry from the normal operating system so that a failure in the normal operations system or path does not affect the redundant system or path.
Redundant system: A system other than the normal operations system, designed to provide communications with the surface when the normal operations path is disrupted. A redundant system may be installed in a separate entry from the normal operating system provided that a failure in the normal operations system or path does not affect the redundant system or path.
Reliability (basic): Basic reliability is a measure of a system's ability to perform its functions without the need for repairs or adjustments. Basic reliability accounts for the time a system or component would be expected to operate without adjustments or repairs and only considers the reliability of the individual components; it does account for the arrangement of components (series versus parallel, for example).
Reliability (operational): The probability that a system can perform and complete its functions satisfactorily. The series or parallel arrangement of components is accounted for in this probability. For example, a redundant design reduces single points of failure and therefore raises the likelihood of the system completing its specified functions, raising the operational reliability.
Repeater: A device placed at intervals in a communications path to receive a signal and then re-transmit at a higher power than received.
Resolution: Tracking system resolution is the smallest change in a miner's location that can be detected or displayed.
Reverse-RFID: An RFID system where the locations of tag and reader are reversed; the tags are located at fixed, known positions within the mine and each miner wears an RFID reader.
RFID (Radio frequency identification): A system that uses radio waves to communicate identification information between a tag and a reader. In a coal mine tracking system, the tag is worn by the miner and readers are placed throughout the mine.
Root node: Point where the wireless network transitions to a wired connection to the mine operations center (MOC) aboveground.
Router: A networking device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers.

S

Scan rate: The frequency with which a tracking system updates location data.
Secondary system: Secondary communications systems operate in non-conventional frequency bands, use large antennas that are best suited for fixed locations or portable applications, and do not have sufficient throughput for general operations. Examples are TTE or MF systems. (MF may perform as a primary system for a small mine.)
Self-healing mesh network or architecture: A mesh network that automatically reconfigures itself if a node fails so that the maximum possible connectivity is maintained.
SHF System: System operating in the Super High Frequency range (3 GHz to 30 GHz).
Shielding: A design approach for keeping undesired EM noise and signals off susceptible equipment by strategic use of materials that reflect RF energy.
Siemens (S): Unit of electrical conductance, one ampere per volt, previously called mho (ohm spelled backwards); S is the reciprocal of resistance (ohm)
Signal propagation characteristics: A technical description of the effects of the environment on the communications signal as it travels between devices.
Signal-to-noise ratio (SNR): The ratio of a signal power to the noise power corrupting the signal. In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise.
Single communications path areas: Areas that do not have dual independent communications paths.
Small mine: A mine which has five or less employees. (MSHA definition).
Spectrum: A range of electromagnetic waves.
Spectrum management: A term that indicates the management of the use of a range of radio frequencies.
Splitter: A device used to maintain proper impedance matching between branches in a leaky feeder system. It can also be used to divide the signal power among each branch in the event that one branch requires more or less power, which is important when designing an efficient communications system.
State-of-charge (SOC): An indication of the amount of remaining available power in the battery, cell, or battery pack as compared to its ideal conditions (new from the manufacturer). It is generally expressed in percent points and is analogous to a fuel gauge in a car.
State-of-health (SOH): A figure of merit of the condition of a battery or cel or battery pack as compared to its ideal conditions, and is generally expressed in percent points - 100% is the original battery from the manufacturer.
Stope antenna: An antenna attached at the end of a leaky feeder cable, sometimes called a termination antenna, which is used to extend the range of radio coverage.
Super high frequency (SHF) system: System operating in the super high frequency range (3 GHz to 30 GHz).
Survivability: The measure of a system's ability to remain operational after an accident.
Susceptibility aspect: . Refers to the correct operation of electronic equipment, referred to as the victim, in the presence of unplanned electromagnetic disturbances. Also referred to as immunity aspect.
System: The working combination of communications or tracking components.

T

Tag: A component in an electronic location systems that transmits unique identification information via radio waves.
Termination antenna: An antenna attached at the end of a leaky feeder cable, sometimes called a stope antenna, which is used to extend the range of radio coverage.
Terminator unit: A component attached to the end of a leaky feeder cable that is used to minimize reflections or undesirable effects due to abrupt changes in cable impedance at its end.
Thermal noise: The electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage.
Thermal runaway: A destructive process experienced by lithium chemistry batteries in which there is a chemical reaction producing a rapid increase in temperature leading to an intense fire and possibly an explosion.
Through-the-earth (TTE) system: A communications system that does not rely on any devices, wires, or structures between the transmitter and receiver.
Time difference of arrival (TDOA): A tracking system method based on the propagation time between a tag and a reader.
Time of flight (TOF): The elapsed time from the instant the signal leaves the transmitter (or source) to the instant it reaches the receiver (or detector).
Topology: A network topology describes the configuration of nodes or components on a network. It defines how they are arranged and connected with each other. Common network topologies include star, ring, line, bus, and tree.
Tracking accuracy: Tracking system accuracy is the measure of error in the miner's reported location
Tracking coverage area: The area of the mine in which the tracking system can provide location information about a miner.
Tracking reporting area: The area where the system is capable of receiving an active reading from the miner's tracking device.
Transceiver: A device that functions as both transmitter and receiver.
Translator: A device which accepts coded electronic pulse information coming from copper wire and then processes and translates that information into equivalently coded light pulses. The process reverses at the other end of the cable, where it converts light pulses back to electronic pulses.
Transmission line: A material structure forming a continuous conducting path from one place to another, directing the transmission of electromagnetic energy with a relatively low loss. The term transmission line includes essentially all types of cables. Examples are telephone lines, power cables, twin lead, coaxial cables, and other similar items.
Transmission medium: The intervening substance through which electromagnetic waves travel.
Transmitter: An electrical device designed to radiate electromagnetic energy.
Transport: One of the two purposes of a network. . In an RFID system the reader transports (or transfers) information from the tag to the mine operation center (MOC). See also access.
Twisted pair: A thin-diameter wire (22 to 26 gauge) commonly used for telephone and network cabling. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pairs have less bandwidth than coaxial cable or fiber-optic cable.
Two-way communications: The ability of the miner's handset to receive and transmit information.

U

Ultrahigh frequency (UHF) system: A system operating in the Ultra High Frequency range (300 to 3000 MHz).
Untethered: A device is considered untethered if there are no cables or wires connected to the device, i.e., cordless.
Up-down frequency converter: A radio frequency upconverter is a device that takes an input of radio frequency (RF) energy of a specific frequency range and outputs it on a higher frequency. Likewise, downconverters take an input frequency and reduce it to a lower output frequency.
Uplink: Pertaining to the transmission path from a mobile station to the base station.
Upstream: Upstream communications is sent from the miner's radio or phone to the mine operations center (MOC). Conversely downstream communications travels from the MOC to the miner's communication device.

V

Very high frequency (VHF) system: A system operating in the Very High Frequency range (30 to 300 MHz).
Victim: A device (e.g., receiver) that is acted on and usually adversely affected by another interfering device.
Voice over Internet Protocol (VoIP): A technology for making telephone calls over the Internet in which speech sounds are converted into binary data.

W

Wavelength: The distance between two consecutive peaks of a wave.
Wi-Fi: Wireless Fidelity. The Wi-Fi Alliance (organization) owns the Wi-Fi (registered trademark) term and specifically defines Wi-Fi as any "wireless local area network (WLAN) products based on the IEEE 802.11 standards."
Wire plant: The collection of conductors in a mine.
Wired system: Used to refer to systems whose components are connected using wires, cables, or fiber-optics. See also hardwired.
Wireless (communications system): 1. A system that operates locally without wires. 2.When used in this tutorial refers to a system where the link between the user and the system is wireless.
Wireless access point (WAP): In computer networking, a wireless access point (WAP) is a device that allows wireless communications devices to connect to a wireless network using Wi-Fi, Bluetooth, or related standards. The WAP usually connects to a wired network, and can relay data from wireless devices.
Wireless local area network (WLAN): A network in which the mobile user can connect to a local area network through a wireless connection. See Local Area Network (LAN).
Working face: The face is the surface where the mining work is advancing.

Y

Yagi antenna: A Yagi (or Yagi-Uda) antenna is a directional antenna consisting of a driven element (typically a dipole) with additional parasitic elements (e.g., reflectors and directors). The reflector element is slightly longer (typically 5% longer) than the driven dipole, whereas the so-called directors are a little bit shorter. This design achieves a very substantial increase in the antenna's directionality and gain as compared to a simple dipole.

Z

ZigBee: A specification for a suite of high level communications protocols using small, low-power digital radios based on the IEEE 802.15.4-2006 standard for wireless personal area networks (WPANs), such as wireless headphones connecting with cell phones via short-range radio.
Zone-based RFID: Each miner wears an RFID tag that transmits a unique identifier. RFID readers are placed throughout the mine. Each reader has its own identification and known location. When a miner passes within range of a reader, the reader interrogates the miner's tag and relays information to the mine operations center (MOC), though the mine's communication system. Based on the relayed information, personnel at the MOC know that the miner is within a certain distance of that reader.