365 results about "Ultra low frequency" patented technology

An underground radio communications and personnel tracking system uses a portable communications device worn by a miner when underground in a mine. A cap-lamp transceiver provides voice and text communication on ultra-low frequency (ULF) to ultra-high frequency (UHF) carrier frequencies and modulation adapted by programming of a software defined radio to making selective and agile radio contacts via through-the-earth, conductor / lifeline, coal seam, tunnel, and ionosphere / earth-surface waveguides for transmission of electromagnetic waves. These waveguides comprise layered earth coal and mineral deposits, and manmade mining complex infrastructures which serendipitously form efficient waveguides. Ultra-Low Frequency F1 / F1 repeaters are placed underground in the mine, and providing for extended range of communication of the cap-lamp transceiver with radios and tracking devices above ground of the mine.

A method for generating electromagnetic waves in the ELF / ULF comprising the steps of using a ground-based Horizontal Electric Dipole (HED) antenna to send electromagnetic pulses upwardly in the E-region of the ionosphere to form an oscillatory or pulsed electric field; allowing said pulsed electric field to interact with magnetized plasma of the lower ionosphere to generate a pulsed horizontal and vertical current which have associated Horizontal and Vertical Electric Dipole moment; and allowing them to radiate.

An occluding hearing aid having anti-occlusion effect techniques combined with at least one improvement which, in the preferred embodiment, includes enhancement of acoustic output in the lower-midrange and bass frequency regions, typically between substantially 40 and 500 Hz, which regions are crucial for natural reproduction of multimedia sound and music but are not optimally processed, and generally not provided at all, in prior art hearing aids in order to avoid exacerbation of the occlusion effect. In specific embodiments, the hearing aid of the present invention includes primary or first microphone exposed to external sound plus a secondary or second microphone exposed to sound within an ear canal, in which a signal produced by the secondary microphone is applied as negative feedback to an input of a non-gain controlling signal process and amplifier driving a hearing aid receiver (transducer), whereby, it has been determined by the present inventor, the occlusion effect may be substantially canceled. The hearing aid further comprises at least one of ten combinational improvements each providing substantial performance benefits over known techniques and devices.

Disclosed is a laser treatment device which is designed to stimulate hair growth and prevent hair loss by applying LLLT (Low Level Laser Therapy) to the scalp using laser light of a specified wavelength. The laser treatment device also provides ultra-low frequency mechanical vibrations to the scalp and the combination of light and vibrations is designed to produce synergy. Laser light, which may be blocked by remaining hair, may nonetheless reach the scalp using light-emitting elements attached to the ends of tooth-shaped protrusions. The present laser treatment device is characterised by a bendable applicator having said tooth-shaped protrusions such that it can change shape in accordance with the curvature of the head, which increase the efficiency of light and vibrational energy delivery. The laser treatment device is optimally controlled with a means to measure the light and vibrational energy supplied to the scalp, and the applicator may also be used as a wearable headset, which provide greater simplicity in mounting and removal.

This invention is an ultra-low frequency electromagnetic telemetry receiver which fuses multiple input receive sources to synthesize a decodable message packet from a noise corrupted telemetry message string. Each block of telemetry data to be sent to the surface receiver from a borehole tool is digitally encoded into a data packet prior to transmission. The data packet is modulated onto the ULF EM carrier wave and transmitted from the borehole to the surface and then are simultaneously detected by multiple receive sensors disbursed within the rig environment. The receive sensors include, but are not limited to, electric field and magnetic field sensors. The spacing of the surface receive elements is such that noise generators are unequally coupled to each receive element due to proximity and / or noise generator type (i.e. electric or magnetic field generators). The receiver utilizes a suite of decision metrics to reconstruct the original, non noise-corrupted data packet from the observation matrix via the estimation of individual data frames. The receiver will continue this estimation process until: 1) the message validates, or 2) a preset “confidence threshold” is reached whereby frames within the observation matrix are no longer “trusted”.

The invention discloses a damping-adjustable vibration isolation platform with quasi-zero stiffness. The damping-adjustable vibration isolation platform comprises a bearing assembly, a fixed platform frame and damping assemblies. The bearing assembly is used for bearing vibration isolation objects. The fixed platform frame is provided with an open end and a cavity which is communicated with the open end, and the bearing assembly and the damping assemblies are contained in the cavity. The damping assemblies comprise the damping-adjustable upper damping assembly and the damping-adjustable lower damping assembly which are arranged in the cavity in the longitudinal direction, and the bearing assembly is connected with the fixed platform frame through the upper damping assembly and the lower damping assembly. The vibration isolation platform solves the difficulty existing when a traditional linear vibration isolation system isolates low frequency or ultra-low frequency vibration, and also overcomes the defects that an active or semi-active control vibration isolation device is complex in structure, high in manufacturing cost, high in energy consumption and the like; the vibration isolation platform is simple in structure, applicable to wide-frequency-domain vibration isolation, capable of being widely applied to precise equipment with strict vibration isolation requirements and has good engineering adaptability. Besides, damping is simple and convenient to adjust.

The invention discloses a parallel mechanism based multidimensional vibration platform. Standard zero stiffness of a vibration isolation platform at the equilibrium position and nonlinear stiffness nearby the equilibrium position can be realized by setting certain structural parameters, and the problem about difficulty in isolating low-frequency or ultra-low-frequency vibration for a traditional linear vibration isolation system; stiffness and damping can be easily and conveniently adjusted, vibration isolation of broad frequency domains are satisfied, and good engineering applicability is achieved; the multidimensional vibration platform is high in bearing stiffness, low in movement stiffness, small in static deflection, low in dynamic inherent frequency and good in vibration isolation effect; inherent contradictions restricting the traditional vibration isolation system, namely the contradictions of low-frequency vibration transmissibility and high-frequency vibration attenuation, can be solved by flexible adjustment of the stiffness and damping; the height and the static equilibrium position of the entire platform can be changed by adjusting a shock absorber spring base in height, and the multidimensional vibration platform is applicable to vibration isolation of objects of different weight.

This invention is an ultra-low frequency electromagnetic telemetry receiver which fuses multiple input receive sources to synthesize a decodable message packet from a noise corrupted telemetry message string. Each block of telemetry data to be sent to the surface receiver from a borehole tool is digitally encoded into a data packet prior to transmission. The data packet is modulated onto the ULF EM carrier wave and transmitted from the borehole to the surface and then are simultaneously detected by multiple receive sensors disbursed within the rig environment. The receive sensors include, but are not limited to, electric field and magnetic field sensors. The spacing of the surface receive elements is such that noise generators are unequally coupled to each receive element due to proximity and / or noise generator type (i.e. electric or magnetic field generators). The receiver utilizes a suite of decision metrics to reconstruct the original, non noise-corrupted data packet from the observation matrix via the estimation of individual data frames. The receiver will continue this estimation process until: 1) the message validates, or 2) a preset “confidence threshold” is reached whereby frames within the observation matrix are no longer “trusted”.

The output of the oscillator is a series of electrical pulses that are typically in the range of 1 to 300 Hz. The open-circuit voltage across the electrodes is typically in the range of 1 to 60 volts, but is current-limited to values that are typically less than 500 uA. These levels are sufficient to provide a safe therapeutic response to the user. The embodiment shown here uses a Clare CPC1824 photovoltaic array and a Texas Instruments LPV7215 comparator configured in a standard oscillator circuit. Other embodiments could use other forms of photovoltaic array. The embodiment shown here is a flat, circular device with a diameter of less than 15 mm and a thickness of less than 5 mm. This makes it well suited as a wearable device that can remain in place for long periods while the user goes about their normal activities.

The invention discloses a sliding elastic beam and spring combined nonlinear ultra-low frequency vibration isolator, which mainly comprises a sliding elastic beam with negative rigidity and a spring with positive rigidity, and is provided with a connection component and a supporting structure, wherein the spring is connected below the sliding elastic beam; the connection component is used for connecting the sliding elastic beam; the supporting structure is used for supporting the sliding elastic beam; the sliding elastic beam has negative rigidity during deformation; the spring is of positive rigidity; and the entire vibration isolator has the characteristic of near zero rigidity because of combination of the two elastic elements. The entire system, namely the sliding beam and spring combined nonlinear ultra-low frequency vibration isolator provided by the invention has the characteristic of approximately dynamic quasi zero rigidity, can be used for isolating vibration of ultra-low frequency and has an anti-impact effect.

The invention provides a petroleum pipeline detecting system which comprises an excitation device, a detecting device, a mileage wheel, a data processing unit, a pipe internal and external data transmission device based on an ultra-low frequency electromagnetic pulse emitter, a low frequency signal emitter based on 22Hz, a low frequency signal receiver based on 22Hz, a driving device, a speed control device, a receiving sensor array, and a data analyzing unit. The system guarantees the stable running of a petroleum pipeline detector by installing a supporting wheel below the pipe internal andexternal data transmission device based on the ultra-low frequency electromagnetic pulse emitter, reduces the situation that detects of the pipeline are undetected by installing the speed control device, improves the locating precision of the pipeline defects by installing a pipe external defect locating device of the low frequency signal generator based on 22Hz, is beneficial to timely finding out defect positions in the pipe by installing the pipe internal and external data transmission device based on the ultra-low frequency electromagnetic pulse emitter.

The invention provides a horizontal two-degree-of-freedom vibration isolating mechanism. The horizontal two-degree of freedom vibration isolating mechanism comprises a connecting plate, wherein a piston rod is inserted in the center of the connecting plate; and four magnetic suspension units are evenly arranged along the circumference of a disc. By utilizing the characteristics of generating the positive rigidity due to like pole repulsion of magnets (comprising electromagnets and permanent magnets) and the negative rigidity due to unlike pole attraction of magnets, the magnetic suspension units are designed to be a horizontal two-degree-of-freedom vibration isolating system with the positive rigidity and the negative rigidity in parallel. Because the positive rigidity and the negative rigidity are in parallel, the positive rigidity and the negative rigidity offset each other, so the horizontal two-degree of freedom vibration isolating mechanism has the self-rigidity close to zero, and the ultra-low frequency horizontal vibration isolation is realized.

An underground radio communications and personnel tracking system uses a cap-lamp worn by a miner when underground in a mine. A cap-lamp transceiver provides voice and text communication on ultra-low frequency (ULF) to ultra-high frequency (UHF) carrier frequencies and modulation adapted by programming of a software defined radio to making selective and agile radio contacts via through-the-earth, conductor / lifeline, coal seam, tunnel, and ionosphere / earth-surface waveguides for transmission of electromagnetic waves. These waveguides comprise layered earth coal and mineral deposits, and manmade mining complex infrastructures which serendipitously form efficient waveguides. Ultra-Low Frequency F1 / F1 repeaters are placed underground in the mine, and providing for extended range of communication of the cap-lamp transceiver with radios and tracking devices above ground of the mine.

The invention relates to a vertical vibration isolation system of single freedom and ultra-low frequency, comprising a mass block, a middle mass block, a zero point generator, a zero stiffness apparatus and a stiffness base. The zero stiffness apparatus invents the dynamic stiffness values of the system at a low cost, which greatly decreases the natural frequency of the system and realizes the passive vibration isolation within the range of ultra-low frequency. The zero point generator reduces the vibration transmissibility in the range of the ultra-low frequency and improves the efficiency of vibration isolation; otherwise, the parameters of the zero point generator can be changed to regulate the system vibration transmissibility according to the actual amplitude and frequency requirements of the vibration isolation. The existing relationship between the zero point generator and the zero stiffness apparatus is: the zero stiffness apparatus decreases the dynamic stiffness value and also brings down the zero value of the zero point generator III and realizes zero within the range of ultra-low frequency.

The utility model relates to an air-floated magnetic motive frictionless suspending device, comprising a frame, a mounting case, a mobile beam, a plurality of guiding bars, a main rod, an air floatation system and a magnetic motive system, wherein, the air floatation system comprises two frictionless cylinders and two air storage tanks of same size; the magnetic motive system comprises a moving coil with a long stroke and the iron core of a exciter; the mounting case is fixed in the middle part of the frame, and a lower mounting plate is positioned in the lower part of the frame; a top plate and a bottom plate are positioned on the mounting plate; two small air bearings for installing the guide bars and a large air bearing for installing the main rod are positioned on the top plate; a large air bearing for installing the guide bars is positioned below the bottom plate; two frictionless cylinders are positioned symmetrically above the mounting plate under the frame; the cylinder rod of the frictionless cylinder is connected with the mobile beam with a connecting hinge; the mobile beam comprises two symmetric parts; the main rod and two guide bars are positioned on the mobile beam; two stop plates are positioned on the two ends of the main rod. The utility model has advantages of meeting the frequency criterion under ultra-low frequency condition, little enough added mass, the small influence of the nonlinearity, and the high testing precision.

The invention relates to an ultra-low frequency alternating-current (AC) constant-current demagnetization device of a large transformer or mutual inductor, comprising a display (1) and a CPU control unit (2), wherein the CPU control unit (2) is connected with a power-frequency signal generator (3); the power-frequency signal generator (3) is connected with a voltage power amplifier (4); the voltage power amplifier (4) is connected with a voltage booster (5); the CPU control unit (2) is also connected with an ultra-low frequency signal generator (6); a switch is arranged between a transformer or a mutual inductor (8) to be tested and the voltage booster (5); and a switch is arranged between the transformer or the mutual inductor (8) to be tested and a current power amplifier (7). The invention overcomes the defects of long demagnetization time, easy transformer coil deformation, and the like of the traditional method and has the advantages of short demagnetization time, light equipment weight, and the like. The invention also discloses a demagnetization detection method adopting the demagnetization device.

A low drop-out voltage regulator having a pass device (Mp), an error amplifier (M1-M51) and a double regulation loop including DC feedback loop (R1, R2) and an AC feedback loop (Rf, Cf) including a high pass filter (Cf). Combining these two loops creates an ultra low frequency internal pole which makes the regulator stable substantially independent of the output bypass capacitor's value. This provides the following advantages: allows the use of very low bypass capacitors; allows to extend the PSRR frequency behavior; allows an increase in the regulator's efficiency (reduced power consumption on heavy loads).

The invention discloses a construction method of a ctDNA ultra-low-frequency mutation detection library, a kit and an analysis method of library detection data. The construction method comprises steps as follows: S1, cfDNA is extracted from whole blood; S2, the terminal of cfDNA is restored and an A basic group is added to the 3'terminal; S3, the terminal of the cfDNA obtained in S2 is connected with connectors containing random label sequences; S4, primers for multiplex PCR (polymerase chain reaction) are designed according to the sequences of the connectors and an object region for object region capturing; S5, a PCR product in S4 is subjected to magnetic bead purification, and small-fragment DNA not subjected to non-specific amplification and primer dimer are removed; S6, a product in S5 is subjected to PCR amplification, an index sequence is introduced, and the ctDNA ultra-low-frequency mutation library is obtained. According to the method, PCR mistakes and sequencing mistakes are eliminated, and the detection specificity is improved.

The invention discloses a water turbine speed regulator PID parameter optimizing method and system. The method comprises the steps that the speed regulator PID parameter optimizing overall objective function J restraining ultra-low frequency oscillation is obtained, optimization is conducted through the optimization algorithm, the optimal PID parameter is sought, and the overall objective function is minimal. According to the method, the value obtained after weighting of the frequency step response deviation absolute value integral and speed regulating system damping at the focused ultra-low frequency band integral serves as the optimization objective, the obtained speed regulator parameter integrates the speed regulator adjusting performance and damping level at the same time, accordingly, the problem of ultra-low frequency oscillation caused by speed regulator negative damping is solved, and the speed regulator adjusting dynamic quality is combined.

The invention provides a design method for a power system stabilizer capable of suppressing ultra-low frequency oscillation. The design method comprises the steps that the operating frequency of the power system stabilizer is divided into an ultra-low frequency band with rotor angular velocity deviation delta omega as input signals and a medium-high frequency band with acceleration power deviation integral as input signals; the input signals of the ultra-low frequency band are screened and subjected to phase compensation; the input signals of the medium-high frequency band are obtained and subjected to phase compensation. According to the design method for the power system stabilizer capable of suppressing ultra-low frequency oscillation, two parallel branch structures are adopted and compensate for different frequency domain ranges respectively, the parameters of the two parallel branch structures are greatly independent with respect to setting, and the problem that an existing PSS is insufficient in damping within an ultra-low frequency domain is solved by means of adding ultra-low frequency branches.

The invention provides a sequencing joint and a preparation method and application thereof in ultra-low frequency mutation detection. The sequencing joint comprises a library amplification primer sequence, a target fragment amplification primer sequence and an error prompting sequence which are connected sequentially, the error prompting sequence is close to one side of a target fragment, the library amplification primer sequence is located on one side away from the target fragment, and the error prompting sequence is the sequence of a known base sequence. The error prompting sequence of the known base sequence is added on one side close to the target fragment, so that the error prompting sequence can add a specific foreign marker on each double-strand DNA template. Following sequencing data of the target fragment can be obtained conveniently, mutation introduced in the sequencing or library amplification step is screened or removed according to the fact whether the sequencing sequences have same error prompting sequences, then the sites with variation in the same positions of the two chains are determined to be real mutation, and the site with the mutation on one chain is identified as the amplification or sequencing error, so that the mutation detection efficiency is improved.

The invention provides a magnetic negative stiffness mechanism with a compact structure, and belongs to the field of ultra-precise vibration damping. The magnetic negative stiffness mechanism includes a frame part, a negative stiffness adjusting part, a flexible guiding part and a moving part. The negative stiffness mechanism utilizes the reverse repelling action of the magnet to form the negative stiffness characteristic, and the size of the negative stiffness can be adjusted through the negative stiffness adjusting part. As the ultra-low frequency vibration damper formed by combining the magnetic negative stiffness mechanism and the positive stiffness spring has extremely low dynamic stiffness, the inherent frequency of the ultra-low frequency vibration damper is greatly reduced, as a result, the vibration damper not only has excellent vibration isolation effect towards the high-frequency vibration interference, but also can effectively isolate the ultra-low frequency vibration, and the magnetic negative stiffness mechanism is applicable to the ultra-precise machining and measuring equipment sensitive to the vibration.

Embodiments of the present invention use an external cavity laser source with dual input terminals, such as bias current for a gain section, and a voltage signal for a modulator section. An aspect of the present invention provides an ultra-low frequency noise external cavity frequency modulated (FM) semiconductor laser source frequency stabilized by a dual electronic feedback circuitry applied to semiconductor gain section and a modulation section. A further aspect of the present invention provides an optical frequency discriminator based on homodyne phase demodulation using an unbalanced Michelson interferometer with fiber optics delay and a symmetrical 3×3 optical coupler.

The invention provides a magnetic suspension type ultra-low-frequency vibration sensor. The magnetic suspension type ultra-low-frequency vibration sensor comprises a housing, a cylindrical permanent magnet, an annular permanent magnet, electromagnetic coils and a photoelectric displacement detector. The conventional spring structure is replaced with a mixed structure of permanent magnetic and electromagnetic, and equivalent support stiffness and equivalent damp of a suspension system are reduced, so that mechanical inherent frequency of the system is effectively reduced, lower limit of ultra-low-frequency band measurement is greatly extended, and the size and the weight of the sensor are reduced. Multiple pairs of symmetric electromagnetic coils are mounted at the bottom of the sensor so as to support a mass block in a suspension way, and the photoelectric displacement detector is adopted to detect displacements in all directions to measure multi-directional torsional vibration parameters so as to further expand application range of the magnetic suspension type ultra-low-frequency vibration sensor. The magnetic suspension type ultra-low-frequency vibration sensor can satisfactorily meet requirements of the fields of national defense industry, aerospace, engineering measurement and the like on ultra-low-frequency vibration measurement, and effectively extends lower limit of ultra-low-frequency vibration measurement.

The invention discloses a positive and negative stiffness parallel quasi-zero stiffness vibration isolator which comprises an upper top plate, a lower top plate, a positive stiffness element and multiple negative stiffness elements, wherein the positive stiffness element and the multiple negative stiffness elements are located between the upper top plate and the lower bottom plate. The positive stiffness element is installed on a base plate, the base plate is fixed to the lower bottom plate and used for adjusting the height of the positive stiffness element, and the multiple negative stiffnesselements are evenly distributed on the left side and the right side of the positive stiffness element. In each negative stiffness element, an inner magnetic ring set and an outer magnetic ring set are both located in a magnetic ring sleeve, the magnetic ring sleeve is fixed to the lower bottom pate, a magnetic ring shaft is located in the axial center of the magnetic ring sleeve, the magnetic ring shaft is fixedly sleeved with the inner magnetic ring set, the inner magnetic ring set is sleeved with the outer magnetic ring set, the outer magnetic ring set is fixed to the magnetic ring sleeve,the top end of the magnetic ring shaft is connected with a metal pulling and pressing rod, the metal pulling and pressing rod is coaxial with the magnetic ring shaft, a pulling and pressing rod pressing block is fixed to the top end of the metal pulling and pressing rod and fixed to the upper top plate, and the inner magnetic ring set and the outer magnetic ring set are axially magnetized. The vibration isolator can achieve ultra-low-frequency vibration isolation.

The invention discloses a quasi-zero stiffness vibration isolator based on a transverse groove spring, and belongs to the field of vibration isolators. An existing linear vibration isolator cannot simultaneously achieve a wide vibration isolation frequency band and small static displacement. According to the quasi-zero stiffness vibration isolator based on the transverse groove spring, a balance position adjustment structure is arranged on the upper surface of a bottom plate of a supporting frame; a positive stiffness mechanism is arranged on the upper part of the balance position adjustment structure; and the periphery of the positive stiffness mechanism is connected to the inner wall of a side face plate of the supporting frame through a set of negative stiffness mechanisms, and the twoends of the negative stiffness mechanisms are connected with the positive stiffness mechanism and the inner wall of the side face plate of the supporting frame through rotating pairs correspondingly.The dynamic stiffness at the balance position is zero, the vibration isolation performance for ultra-low frequency vibration is improved, and the effect of full frequency band isolation can further beachieved especially for basic excitation.

A follow-up air-floating magnetic frictionless suspension device, including an installation frame, a moving beam, a guide rod, an air flotation system and a magnetic system, the air flotation system includes two frictionless cylinders, two air storage tanks, no The friction cylinder is connected to the air pipe, precision pressure reducing valve, and air intake pipe; the magnetic system includes a long-stroke moving coil and an exciter iron core; two friction-free cylinders are symmetrically installed above the bottom plate of the installation frame, and the friction-free cylinder The frictionless cylinder is connected to the air pipe with the air storage tank. The compressed air source is connected to the air storage tank through a precision pressure reducing valve and the air source intake pipe. The piston rod of the frictionless air cylinder is connected to the moving beam through a connecting hinge. The air bearing is installed on the guide rod, the guide rod is fixedly installed on the installation frame, the air path in the moving beam is connected to the air bearing, and a suspension rod is fixed below the moving beam. The invention can also meet the frequency criterion at the time of ultra-low frequency, the additional mass is small enough, the non-linear influence is small, and the test precision is high.

The invention relates to a prime mover speed control system additional damper control method. The mechanical power which affects the prime mover speed control system is calculated according to a pre-defined prime mover speed control system model. The mechanical power is decomposed into damping torque and synchronization torque components, so as to acquire compensated additional damping coefficients under power closed-loop adjustment and rotation speed closed-loop adjustment. According to the additional damping coefficients, the damping torque interval is determined. A speed control system additional damper model is built to carry out phase compensation on a compensation link corresponding to the phase frequency characteristic of the speed control system, so that the additional damping coefficients are positive. According to the invention, ultra-low frequency oscillation damping caused by the speed control system is improved.

The invention provides a low-frequency communication system of a rotating electret mechanical antenna, belonging to the technical field of low-frequency communication. The system of the invention comprises a low-frequency magnetic field signal generating module and a magnetic induction signal receiving module. The low frequency magnetic field signal generation module comprises a motor and a charged electret in a mechanical antenna; the motor in the mechanical antenna is controlled to produce different rotational speed, electret is driven to rotate, magnetic field signals of different frequencies are produced. A desired communication signal is loaded onto the generated magnetic field signal, and the signal is transmitted to the receiving direction by a mechanical antenna. The magnetic induction signal receiving module receives the transmitted magnetic field signal through the magnetic field sensor, and demodulates and acquires the required communication signal. The invention utilizes the characteristics of ultra-low frequency and very-low frequency radio waves, adopts the method that a motor drives a charged electret to rotate, forms a low-frequency alternating magnetic field and transmits a magnetic field signal, can greatly reduce the antenna length and power consumption of a radio transmitter, and realizes stable low-frequency radio communication.

An underground radio communications and personnel tracking system uses a portable communications device worn by a miner when underground in a mine. A cap-lamp transceiver provides voice and text communication on ultra-low frequency (ULF) to ultra-high frequency (UHF) carrier frequencies and modulation adapted by programming of a software defined radio to making selective and agile radio contacts via through-the-earth, conductor / lifeline, coal seam, tunnel, and ionosphere / earth-surface waveguides for transmission of electromagnetic waves. These waveguides comprise layered earth coal and mineral deposits, and manmade mining complex infrastructures which serendipitously form efficient waveguides. Ultra-Low Frequency F1 / F1 repeaters are placed underground in the mine, and providing for extended range of communication of the cap-lamp transceiver with radios and tracking devices above ground of the mine.