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Where Are We Now, and Where Are We Going? In this month’s column, we travel along the road of PPP development, examine its current status and look at where it might go in the near future By Sunil Bisnath, John Aggrey, Garrett Seepersad and Maninder Gill Innovation Insights with Richard Langley PPP. It’s one of the many acronyms (or initialisms, if you prefer) associated with the uses of global navigation satellite systems. It stands for precise point positioning. But what is that? Isn’t all GNSS positioning precise? Well, it’s a matter of degree. Take GPS, for example. The most common kind of GPS signal use, that implemented in vehicle “satnav” units; mobile phones; and hiking, golfing and fitness receivers, is to employ the L1 C/A-code pseudorange (code) measurements along with the broadcast satellite orbit and clock information to produce a point position. Officially, this is termed use of the GPS Standard Positioning Service (SPS). It is capable of meter-level positioning accuracy under the best conditions. There is a second official service based on L1 and L2 P-code measurements and broadcast data called the Precise Positioning Service (PPS). In principle, because the P-code provides somewhat higher precision code measurements and the use of dual-frequency data removes virtually all of the ionospheric effect, PPS is capable of slightly more precise (and accurate) positioning. But because the P-code is encrypted, PPS is only available to so-called authorized users. While meter-level positioning accuracy is sufficient for many, if not most applications, there are many uses of GNSS such as machine control, surveying and various scientific tasks, where accuracies better than 10 centimeters or even 1 centimeter are needed. Positioning accuracies at this level can’t be provided by pseudoranges alone and the use of carrier-phase measurements is required. Phase measurements are much more precise than code measurements although they are ambiguous and this ambiguity must be estimated and possibly resolved to the correct integer value. Traditionally, phase measurements (typically dual-frequency) made by a potentially moving user receiver have been combined with those from a reference receiver at a well-known position to produce very precise (and accurate) positions. If done in real time (through use of a radio link of some kind), this technique is referred to as real-time kinematic or RTK. A disadvantage of RTK positioning is that it requires reference station infrastructure including a radio link (such as mobile phone communications) for real-time results. Is there another way? Yes, and that’s PPP. PPP uses the more precise phase measurements (along with code measurements initially) on at least two carrier frequencies (typically) from the user’s receiver along with precise satellite orbit and clock data derived, by a supplier, from a global network. Precision, in this case, means a horizontal position accuracy of 10 centimeters or better. In this month’s column, we travel along the road of PPP development, examine its current status, and look at where it might go in the near future. In a 2009 GPS World “Innovation” article co-authored by Sunil Bisnath, the performance and technical limitations at the time of the precise point positioning (PPP) GPS measurement processing technique were described and a set of questions asked about the potential of PPP, especially with regard to the real-time kinematic (RTK) measurement processing technique. Since the 2009 article, we’ve seen a significant amount of research and development (R&D) activity in this area. Many scientific papers discuss PPP and making use of PPP — a search on Google Scholar for “GNSS PPP” delivers nearly 7,000 results, and for “GPS PPP” more than 15,000 results! Will PPP eventually overtake RTK as the de facto standard for precise (that is, few centimeter-level) positioning? Or, in light of PPP R&D developments, should we be asking different questions, such as will multiple precise GNSS positioning techniques compete or complement each other or perhaps result in a hybrid approach? In almost a decade, have we seen much in the way of positioning performance improvement, where “performance” can refer to positioning precision, accuracy, availability and integrity? Or, to some users, has the Achilles’ heel of PPP — the initial position solution convergence period — only been reduced from, for example, 20 minutes to 19 minutes? From such a perspective, all of this PPP research might not appear to have produced much tangible benefit. Advances have been made from this research and we will explore them here. Also, aside from many researchers working diligently on their own PPP software, there are now a number of well-established PPP-based commercial services — a number that has grown and been affected by the wave of GNSS industry consolidation over the decade. Consequently, there is much more to this story. This month’s article summarizes the current status of PPP performance and R&D, and discusses the potential future of the technique. In the first part of the article, we will present brief explanations of conventional dual-frequency PPP, recent research and implementations, and application of the evolved technique to low-cost hardware. We will conclude the article with a rather dangerous attempt at near-term extrapolation of potential upcoming developments and conceivable implications. Conventional PPP The concept of PPP is based on standard, single-receiver, single-frequency point positioning using pseudorange (code) measurements, but with the meter-level satellite broadcast orbit and clock information replaced with centimeter-level precise orbit and clock information, along with additional error modeling and (typically) dual-frequency code and phase measurement filtering. Back in 1995, researchers at Natural Resources Canada were able to reduce GPS horizontal positioning error from tens of meters to the few-meter level with code measurements and precise orbits and clocks in the presence of Selective Availability (SA). Subsequently, the Jet Propulsion Laboratory introduced PPP as a method to greatly reduce GPS measurement processing time for large static networks. When SA was turned off in May 2000 and GPS satellite clock estimates could then be more readily interpolated, the PPP technique became scientifically and commercially popular for certain precise applications. Unlike static relative positioning and RTK, conventional PPP does not make use of double-differencing, which is the mathematical differencing of simultaneous code and phase measurements from reference and remote receivers to greatly reduce or eliminate many error sources. Rather, PPP applies precise satellite orbit and clock corrections estimated from a sparse global network of satellite tracking stations in a state-space version of a Hatch filter (in which the noisy, but unambiguous, code measurements are filtered with the precise, but ambiguous, phase measurements). This filtering is illustrated in FIGURE 1, where measurements are continually added in time in the range domain, and errors are modeled and filtered in the position domain, resulting in reduced position error in time. FIGURE 1. Illustration of conventional PPP measurement and error modeling in state-space Hatch filter, resulting in reduced position error in time. The result is the characteristic PPP initial convergence period seen in FIGURE 2, where the position solution is initialized as a sub-meter, dual-frequency code point positioning solution, quickly converging to the decimeter-level in something like 5 to 20 minutes, and a few centimeters after ~20 minutes when geodetic-grade equipment is used (at station ALGO, Algonquin Park, Canada, on Jan. 2, 2017). For static geodetic data, daily solutions are typically at the few millimeter-level of accuracy in each Cartesian component. FIGURE 2. Conventional geodetic GPS PPP positioning performance characteristics of initial convergence period and steady state for station ALGO, Algonquin Park, Canada, on Jan. 2, 2017. The primary benefit of conventional PPP is that with the use of state-space corrections from a sparse global network, there is the appearance of precise positioning from only a single geodetic receiver. Therefore, baseline or network RTK limitations are removed in geographically challenging areas, such as offshore, far from population centers, in the air, in low Earth orbit, and so on, and without the need for the requisite terrestrial hardware and software infrastructure. PPP is now the de facto standard for precise positioning in remote areas or regions of low economic density, which limit or prevent the use of relative GNSS, RTK or network RTK, but allow for continuous satellite tracking. These benefits translate into the main commercial applications of offshore positioning, precision agriculture, geodetic surveys and airborne mapping, which also are not operationally bothered by initial convergence periods of tens of minutes. For urban and suburban applications, RTK and especially network RTK allow for near-instantaneous, few-centimeter-level positioning with the use of reference stations and regional satellite (orbit and clock) and atmospheric corrections. The use of double-differencing and these local or regional corrections allows sufficient measurement error mitigation to resolve double-differenced phase ambiguities. All of this additional information is not available to conventional PPP, limiting its precise positioning performance, but which is considered in PPP enhancements. Progress on PPP Convergence Limitations Over the past decade or so, PPP R&D activity can be categorized as follows: Integration of measurements from multiple GNSS constellations, transitioning from GPS PPP to GNSS PPP; Resolution of carrier-phase ambiguities in PPP user algorithms — in an effort to increase positional accuracy and solution stability, but foremost in an effort to reduce the initial convergence period; and Use of a priori information to reduce the initial convergence and re-convergence periods and improve solution stability, making use of available GNSS error modeling approaches. Unlike relative positioning, which makes use of measurements from the user receiver as well as the reference receiver, PPP only relies on measurements from the user site. This situation results in weaker initial geometric strength, and so the addition of more unique measurements is welcome. To make use of measurements from all four GNSS constellations (GPS, GLONASS, Galileo and BeiDou), user-processing engines must account for differences in spatial and temporal reference systems between constellations and numerous equipment delays between frequencies and modulations. The former can be done so that any number of measurements from any number of constellations can be processed to produce one unique PPP position solution. The latter requires a great deal of calibration, especially for heterogeneous tracking networks and user equipment (antenna, receiver and receiver firmware), most notably for the current frequency division multiple access GLONASS constellation. FIGURE 3 shows typical multi-GNSS float (non-ambiguity-fixed) horizontal positioning performance at multi-GNSS station GMSD in Nakatane, Japan, on March 24, 2017. As with all modes of GNSS data processing, more significant improvement with additional constellations can be seen in sky-obstructed situations. FIGURE 3. Typical conventional multi-GNSS PPP float horizontal positioning accuracy for station GMSD, Nakatane, Japan, March 24, 2017 (G: GPS, R: GLONASS, E: Galileo and C: BeiDou). Related to multi-constellation processing is triple-frequency processing afforded by the latest generation of GPS satellites and the Galileo and BeiDou constellations. More frequencies mean more measurements, although with the same satellite-to-receiver measurement geometry as dual-frequency measurements. Again, additional signals require additional equipment delay modeling, in this case especially for the processing of GPS L1, L2 and L5 observables. For processing of four-constellation data available from 20 global stations in early 2016, FIGURE 4 shows the average reduction of float (non-ambiguity-fixed) horizontal error from dual- to triple-frequency processing of approximately 40% after the first five minutes of measurement processing. In terms of positioning, this result, for this time period with a limited number of triple-frequency measurements, means a reduction in average horizontal positioning error from 43 to 26 centimeters within the first five minutes of data collection. FIGURE 4. Average dual- and triple-frequency static, float PPP horizontal solution accuracy for 20 global stations. Data collected from tracked GPS, GLONASS, Galileo and BeiDou satellites in early 2016. PPP with ambiguity resolution, or PPP-AR, was seen as a potential solution to the PPP initial solution convergence “problem” analogous to AR in RTK. Various researchers put forward methods, in the form of expanded measurement models, to isolate pseudorange and carrier-phase equipment delays to estimate carrier-phase ambiguities. These methods remove receiver equipment delays through implicit or explicit between-satellite single-differencing and estimate satellite equipment delays in the network product solution either as fractional cycle phase biases or altered clock products. FIGURE 5 illustrates the difference between a typical GPS float and fixed solution (for station CEDU, Ceduna, Australia, on June 28, 2017). Initial solution convergence time is reduced, and stable few-centimeter-level solutions are reached sooner. For lower quality data, ambiguity fixing does not provide such quick initial solution convergence. Fixing is dependent on the quality of the float solution; and, for PPP, the latter requires time to reach acceptable levels of accuracy. Therefore, depending on the application, PPP-AR may or may not be helpful. FIGURE 5. Typical float (red) and fixed (pink) GPS PPP horizontal solution error at geodetic station CEDU, Ceduna, Australia, on June 28, 2017. To consistently reduce the initial solution convergence period, PPP processing requires additional information, as is the case for network RTK, in which interpolated satellite orbit, ionospheric and tropospheric corrections are needed since double-differenced RTK baselines over 10 to 15 kilometers in length contain residual atmospheric errors too large to effectively and safely resolve phase integer ambiguities. For PPP, uncombining the ionospheric-free code and phase measurements from the conventional model is required, to directly estimate slant ionosphere propagation terms in the filter state. In this form, the model can allow for very quick re-initialization of short data gaps by using the pre-gap slant ionospheric (and zenith tropospheric) estimates as down-weighted a priori estimates post-gap — making these estimates bridging parameters in the estimation filter. Expanding this approach, external atmospheric models can be used to aid with initial solution convergence. FIGURE 6 illustrates, for a large dataset, that applying a spatially and temporally coarse global ionospheric map (GIM) to triple-frequency, four-constellation float processing can reduce one-sigma convergence time to 10 centimeters horizontal positioning error from 16 to 6 minutes. If local ionospheric (and tropospheric) corrections are available and AR is applied, PPP (sometimes now referred to as PPP-RTK) can produce RTK-like results with a few minutes of initial convergence to few-centimeter-level horizontal solutions. FIGURE 6. Averaged horizontal error from 70 global sites in mid-2016 using four-constellation, triple-frequency processing. PPP Processing with Low-Cost Hardware As the impetus for low-cost, precise positioning and navigation for autonomous and semi-autonomous platforms (such as land vehicles and drones) continues to grow, there is interest in processing such low-cost data with PPP algorithms. For example, it has been shown that with access to single-frequency code and phase measurements from a smartphone, short-baseline RTK positioning is possible. It has also been shown that similar smartphone data can be processed with the PPP approach. From the origins of PPP, it may be argued that single-frequency processing and many-decimeter-level positioning performance is not “precise.” But we will avoid such semantic arguments here (but see “Insights”), and focus on the use of high-performance measurement processing algorithms to new low-cost hardware. We are currently witnessing great changes in the GNSS chip market: single-frequency chips for tens-of-dollars or less; and boards with multi-frequency chips for hundreds-of-dollars. And these chips will continue to undergo downward price pressure with increases in capability, and be further enabled for raw measurement use in a wider range of applicable technology solutions. There are now a number of low-cost, dual-frequency, multi-constellation products on the market, with additional such products as well as smartphone chips coming soon. To process data from such products with a PPP engine, modifications are required to optimally account for single-frequency measurements in the estimation filter, optimize the measurement quality control functions for the much noisier code and phase measurements compared to data from geodetic receivers, and optimize the stochastic modeling for the much noisier code and phase measurements. The single-frequency measurement model can be modified to either make use of the Group and Phase Ionospheric Calibration linear combination (commonly referred to as GRAPHIC) or ingest data from an ionospheric model. Due to the use of low-cost antennas, as well as the low-cost chip signal processing hardware, code and phase measurements suffer from significant multipath and noise at lower signal strengths; therefore, outlier detection functions must be modified. Also, the relative weighting of code and phase measurements must be customized for more realistic low-cost data processing. FIGURE 7 compares the carrier-to-noise-density ratio (C/N0) values from ~1.5 hours of static GPS L1 signals collected from a geodetic receiver with a geodetic antenna, a low-cost receiver chip with a patch antenna, and a tablet chip and internal antenna, as a function of elevation angle. Received signal C/N0 values can be used as a proxy for signal precision. The three datasets were collected at the same time in mid-September 2017 in Toronto, Canada, with the receivers and antennas within a few meters of each other. The shading represents the raw estimates output from each receiver, while the solid lines are moving-average filtered results. FIGURE 7. Carrier-to-noise-density ratios of ~1.5 hour of static GPS L1 signals from a geodetic receiver with a geodetic antenna, a low-cost receiver chip with a patch antenna, and a tablet chip and internal antenna, as a function of elevation angle. Keeping in mind the log nature of C/N0, the high measurement quality of the geodetic antenna and receiver are clear. The low-cost chip and patch antenna signal strength structure is similar, but, on average, 3.5 dB-Hz lower. And the tablet received signal strength is lower still, on average a further 4.0 dB-Hz lower, with greater degradation at higher signal elevation angles and much greater signal strength variation. The PPP horizontal position uncertainty for these datasets is shown in FIGURE 8. Note that reference coordinates have been estimated from the datasets themselves, so potential biases, in especially the low-cost and tablet results, can make these results optimistic. Given that only single-frequency GPS code and phase measurements are being processed, initial convergence periods are short and horizontal position error reaches steady state in the decimeter range. The geodetic and the low-cost results are comparable at the 2-decimeter level, whereas the tablet results are worse, at the approximately 4-decimeter level. Initial convergence of the geodetic solution is superior to the others, driven by the higher quality of its code measurements. The grade of antenna plays a large role in the quality of these measurements, for which there are physical limitations in design and fabrication. While geodetic antennas can be used, this is not always feasible, given the mass limitations of certain platforms or the cost limitations for certain applications. FIGURE 8. Horizontal positioning error (compared to final epoch solutions) for geodetic, low-cost and tablet data processed with PPP software customized for single-frequency and less precise measurements. Comments Regarding the Near Future The PPP GNSS measurement processing approach was originally designed to greatly reduce computation burden in large geodetic networks of receivers by removing the need for network baseline processing. The technique found favor for applications in remote areas or regions with little terrestrial infrastructure, including the absence of GNSS reference stations. Given PPP’s characteristic use of a single receiver for precise positioning, various additional augmentations have been made to remove or reduce solution initialization and re-initialization interval to near RTK-like levels. But, to what end? This question can be approached from multiple perspectives. From the theoretical standpoint, there is the impetus to maximize performance — millimeter-level static positioning over many hours, and few-centimeter-level kinematic positioning in a few minutes — by augmenting PPP in any way necessary. There is the academic exercise of maximizing performance without the need for local or regional reference stations – apparent single-receiver positioning, or truly wide-area augmentation. In terms of engineering problems, we can work to do more with less, that is, decimeter-level positioning with ultra-low-cost hardware, or the same with less, that is, few-centimeter-level positioning with low-cost hardware. And from the practical or commercial aspect, the great interest is for the implementation of evolved PPP methods for applications that can efficiently and effectively make use of the technology. In terms of service providers, be it regional or global, commercial or public, there is momentum to provide enhanced correction products that are blurring the lines across the service spectrum from constellation-owner tracking to regional, terrestrial augmentation. A public GNSS constellation-owner, through its constellation tracking network, can provide PPP-like corrections and services. A global commercial provider with or without regional augmentation can provide similar services. The key is providing multi-GNSS state-space corrections for satellite orbits, satellite clocks, satellite equipment delays (fractional phase biases), zenith ionospheric delay and zenith tropospheric delay at the temporal and spatial resolution necessary for the desired positioning performance at reasonable cost, that is, subscription fees that particular markets can bear. Given these correction products, PPP users have a greater ability to access a wide array of positioning performance levels for various new applications, be it few-decimeter-level positioning on mobile devices to few-centimeter-level positioning for autonomous or semi-autonomous land, sea and air vehicles. PPP can be used for integrity monitoring and perhaps safety-of-life applications where low-cost is a necessity and relatively precise positioning for availability and integrity purposes is required. For safety critical and high-precision applications, such as vehicle automation, PPP can be used alongside, or in combination with, RTK for robustness and independence with low-cost hardware. Such a parallel and collaborative approach would require a hybrid user processing engine and robust state-space corrections from a variety of local, regional and global sources, as we are seeing from some current geodetic hardware-based commercial services. Near-future trends should also include more low-cost, multi-sensor integration with PPP augmentation. Optimized navigation algorithms and efficient user processing engines will be a priority as the capabilities of low-cost equipment continue to increase and low-cost integrated sensor solutions are required for mass-market applications. Analogous to meter-level point position GNSS, lower hardware costs should drive markets to volume sales, PPP-like correction services, and GNSS-based multi-sensor integration into more navigation technology solutions for various industry and consumer applications. Clearly, the future of PPP continues to be bright. SUNIL BISNATH is an associate professor in the Department of Earth and Space Science and Engineering at York University, Toronto, Canada. For over twenty years, he has been actively researching GNSS processing algorithms for a wide variety of positioning and navigation applications. JOHN AGGREY is a Ph.D. candidate in the Department of Earth and Space Science and Engineering at York University. He completed his B.Sc. in geomatics at Kwame Nkrumah University of Science and Technology, Ghana, and his M.Sc. at York University. His research currently focuses on the design, development and testing of GNSS PPP software, including functional, stochastic and error mitigation models. GARRETT SEEPERSAD is a navigation software design engineer for high-precision GNSS at u-blox AG and concurrently is completing his Ph.D. in the Department of Earth and Space Science and Engineering at York University. His Ph.D. research focuses on GNSS PPP and ambiguity resolution. He completed his B.Sc. in geomatics at the University of the West Indies in Trinidad and Tobago. He holds an M.Sc. degree in the same field from York University. MANINDER GILL is a geomatics designer at NovAtel Inc. and concurrently is completing his M.Sc. in the Department of Earth and Space Science and Engineering at York University. His M.Sc. research focuses on GNSS PPP and improving positioning accuracy for low-cost GNSS receivers. He holds a B.Eng. degree in geomatics engineering from York University. FURTHER READING • Comprehensive Discussion of Technical Aspects of Precise Point Positioning “Precise Point Positioning” by J. Kouba, F. Lahaye and P. Tétreault, Chapter 25 in Springer Handbook of Global Navigation Satellite Systems, edited by P.J.G. Teunissen and O. Montenbruck, published by Springer International Publishing AG, Cham, Switzerland, 2017. • Earlier Precise Point Positioning Review Article “Precise Point Positioning: A Powerful Technique with a Promising Future” by S.B. Bisnath and Y. Gao in GPS World, Vol. 20, No. 4, April 2009, pp. 43–50. • Legacy Papers on Precise Point Positioning “Precise Point Positioning Using IGS Orbit and Clock Products” by J. Kouba and P. Héroux in GPS Solutions, Vol. 5, No. 2, October 2001, pp. 12–28, doi: 10.1007/PL00012883. “GPS Precise Point Positioning with a Difference” by P. Héroux and J. Kouba, a paper presented at Geomatics ’95, Ottawa, Canada, 13–15 June 1995. “Precise Point Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks” by J.F. Zumberge, M.B. Heflin, D.C. Jefferson, M.M. Watkins and E.H. Webb in Journal of Geophysical Research, Vol. 102, No. B3, pp. 5005–5017, 1997, doi: 10.1029/96JB03860. • Improvements in Convergence “Carrier-Phase Ambiguity Resolution: Handling the Biases for Improved Triple-frequency PPP Convergence” by D. Laurichesse in GPS World, Vol. 26, No. 4, April 2015, pp. 49-54. “Reduction of PPP Convergence Period Through Pseudorange Multipath and Noise Mitigation” by G. Seepersad and S. Bisnath in GPS Solutions, Vol. 19, No. 3, March 2015, pp. 369–379, doi: 10.1007/s10291-014-0395-3. “Global and Regional Ionospheric Corrections for Faster PPP Convergence” by S. Banville, P. Collins, W. Zhang and R.B. Langley in Navigation, Vol. 61, No. 2, Summer 2014, pp. 115–124, doi: 10.1002/navi.57. “A New Method to Accelerate PPP Convergence Time by Using a Global Zenith Troposphere Delay Estimate Model” by Y. Yao, C. Yu and Y. Hu in The Journal of Navigation, Vol. 67, No. 5, September 2014, pp. 899–910, doi: 10.1017/S0373463314000265. “External Ionospheric Constraints for Improved PPP-AR Initialisation and a Generalised Local Augmentation Concept” by P. Collins, F. Lahaye and S. Bisnath in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, Sept. 17–21, 2012, pp. 3055–3065. • Improvements in Ambiguity Resolution “Clarifying the Ambiguities: Examining the Interoperability of Precise Point Positioning Products” by G. Seepersad and S. Bisnath in GPS World, Vol. 27, No. 3, March 2016, pp. 50–56. “Integer Ambiguity Resolution on Undifferenced GPS Phase Measurements and Its Application to PPP and Satellite Precise Orbit Determination” by D. Laurichesse and F. Mercier, J.-P. Berthias, P. Broca and L. Cerri in Navigation, Vol. 56, No. 2, Summer 2009, pp. 135–149. “Resolution of GPS Carrier-phase Ambiguities in Precise Point Positioning (PPP) with Daily Observations” by M. Ge, G. Gendt, M. Rothacher, C. Shi and J. Liu in Journal of Geodesy, Vol. 82, No. 7, July 2008, pp. 389–399, doi: 10.1007/s00190-007. Erratum: doi: 10.1007/s00190-007-0208-3. “Isolating and Estimating Undifferenced GPS Integer Ambiguities” by P. Collins in Proceedings of ION NTM 2008, the 2008 National Technical Meeting of The Institute of Navigation, San Diego, California, Jan. 28–30, 2008, pp. 720–732. • Precise Positioning Using Smartphones “Positioning with Android: GNSS Observables” by S. Riley, H. Landau, V. Gomez, N. Mishukova, W. Lentz and A. Clare in GPS World, Vol. 29, No. 1, January 2018, pp. 18 and 27–34. “Precision GNSS for Everyone: Precise Positioning Using Raw GPS Measurements from Android Smartphones” by S. Banville and F. van Diggelen in GPS World, Vol. 27, No. 11, November 2016, pp. 43–48. “Accuracy in the Palm of Your Hand: Centimeter Positioning with a Smartphone-Quality GNSS Antenna” by K.M. Pesyna, R.W. Heath and T.E. Humphreys in GPS World, Vol. 26, No. 2, February 2015, pp. 16–18 and 27–31.

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custom team designs to,condor wp05120i ac adapter 12v dc 500ma power supply.soft starter for 3 phase induction motor using microcontroller.videonow dc car adapter 4.5vdc 350ma auto charger 12vdc 400ma fo.dell pa-2 ac adapter 20vdc 3.5a ite power supply 85391 zvc70ns20,we were walking at the beach and had to hide and cover our children,including almost all mobile phone signals.zte stc-a22o50u5-c ac adapter 5vdc 700ma used usb port plug-in d,qc pass e-10 car adapter charger 0.8x3.3mm used round barrel.dve dsa-0051-03 fus ac adapter 5vdc 0.5a mini usb charger,chd scp0500500p ac adapter 5vdc 500ma used -(+)- 0.5 x 2.4 x 9 m,cs cs-1203000 ac adapter 12vdc 3a used -(+) 2x5.5mm plug in powe.stancor sta-4190d ac adapter 9vac 500ma used 2x5.4mm straight ro,replacement 1650-05d ac adapter 19.5v 3.34a used -(+)- 5x7.4mm r,can be adjusted by a dip-switch to low power mode of 0,qualcomm cxdtc051 ac adapter 8.4dc 1025ma ac power supply,4.5v-9.5vdc 100ma ac adapter used cell phone connector power sup,here is the circuit showing a smoke detector alarm.delta sadp-65kb d ac adapter 19v dc 3.42a used 2.3x5.5x9.7mm,acbel api-7595 ac adapter 19vdc 2.4a for toshiba 45 watt global,ktec ksas7r50900050d5 ac adapter 9vdc 0.5a used -(+) 1.8x5.5x9mm,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.hy2200n34 ac adapter 12v 5vdc 2a 4 pin 100-240vac 50/60hz,nikon mh-23 ac adapter 8.4vdc 0.9a 100-240vac battery charger po,fuji fujifilm cp-fxa10 picture cradle for finepix a310 a210 a205,voyo xhy050200lcch ac adapter 5vdc 2a used 0.5x2.5x8mm round bar.ibm pscv 360107a ac adapter 24vdc 1.5a used 4pin 9mm mini din 10,delta adp-90sb bb ac adapter 19vdc 4.74a -(+) 2.5x5.5mm used 100,cs-6002 used ac grill motor 120vac 4w e199757 214624 usa canada,lf0900d-08 ac adapter 9vdc 200ma used -(+) 2x5.5x10mm round barr.it works well for spaces around 1.pride mobility elechg1024 ea1089a ac acid battery charger adapte,rca cps015 ac adapter9.6vdc 2.3a 12.5v 1.6a used camcorder bat,craftsman 982245-001 dual fast charger 16.8v cordless drill batt,phihong psa31u-050 ac adapter 5vdc 4a used -(+)- 5 pin din ite p,nikon eh-69p ac adapter 5vdc 0.55a used usb i.t.e power supply 1,cet 41-18-300d ac dc adapter 18v 300ma power supply.southwestern bell freedom phone 9a300u ac adapter 9vac 300ma,olympus li-40c li-ion battery charger 4.2vdc 200ma for digital c,ad-0950-cs ac adapter 9vdc 500ma used -(+) 2x5.5x11mm round barr,sony dcc-fx110 dc adapter 9.5vdc 2a car charger for dvpfx810.adp da-30e12 ac adapter 12vdc 2.5a new 2.2 x 5.5 x 10 mm straigh.one is the light intensity of the room.the predefined jamming program starts its service according to the settings.mobile jammer can be used in practically any location.v-2833 2.8vdc 165ma class 2 battery charger used 120vac 60hz 5w,nyko aspw01 ac adapter 12.2vdc 0.48a used -(+) 2x5.5x10mm round,mbsc-dc 48v-2 ac adapter 59vdc 2.8a used -(+) power supply 100-1,the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer.dell da90pe3-00 ac adapter 19.5v 4.62a pa-3e laptop power suppl,dream gear md-5350 ac adapter 5vdc 350ma for game boy advance.rs18-sp0502500 ac adapter 5vdc 1.5a -(+) used 1x3.4x8.4mm straig,black & decker 371415-11 ac adapter 13vdc 260ma used -(+) 2x5.5m.replacement ppp003sd ac adapter 19v 3.16a used 2.5 x 5.5 x 12mm.ibm thinkpad 73p4502 ac dc auto combo adapter 16v 4.55a 72w.a mobile jammer is an instrument used to protect the cell phones from the receiving signal,super mobilline 12326 mpc 24vdc 5a charger 3pin xlr male used de.skynet hyp-a037 ac adapter 5vdc 2400ma used -(+) 2x5.5mm straigh,smoke detector alarm circuit,273-1454 ac adapter 6vdc 200ma used 2.2x5.5mm 90 degree round ba,advent t ha57u-560 ac adapter 17vdc 1.1a -(+) 2x5.5mm 120vac use,lite-on pa-1700-02 ac adapter 19vdc 3.42a used 2x5.5mm 90 degr.kodak k8500 li-on rapid battery charger dc4.2v 650ma class 2.artesyn scl25-7624 ac adapter 24vdc 1a 8pin power supply,cybiko ac adapter 5v dc 300ma used usb connector class 2 power u.


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T027 4.9v~5.5v dc 500ma ac adapter phone connector used travel.the unit requires a 24 v power supply,all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer.delta adp-40wb ac adapter 12vdc 3330ma -(+) 2x5.5mm used 100-240.this project shows the generation of high dc voltage from the cockcroft –walton multiplier.000 (67%) 10% off on icici/kotak bank cards,viii types of mobile jammerthere are two types of cell phone jammers currently available.fineness power spp34-12.0-2500 ac adapter 12vdc 2500ma used 4 pi,braun 4728 base power charger used for personal plaque remover d.the black shell and portable design make it easy to hidden and use,hp pa-1650-02hp ac adapter 18.5v 3.5a 65w used 1.5x4.8mm.anoma aspr0515-0808r ac adapter 5vdc 0.8a 15vdc 0.75a 5pin molex,hewlett packard series ppp009h 18.5v dc 3.5a 65w -(+)- 1.8x4.7mm,casio ad-5ul ac adapter 9vdc 850ma used +(-) 2x5.5x9.7mm 90°righ.th 5vdc 11v used travel charger power supply 90-250vac phone,finecom 12vdc 1a gas scooter dirt bike razor charger atv 12 volt,thomson 5-4026a ac adapter 3vdc 600ma used -(+) 1.1x3.5x7mm 90°.apple macintosh m7778 powerbook duo 24v 1.04a battery recharher.tc98a 4.5-9.5v dc max 800ma used travel charger power supply.5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,apd da-2af12 ac adapter used -(+)2x5.5mm 12vdc 2a switching powe.databyte dv-9319b ac adapter 13.8vdc 1.7a 2pin phoenix power sup,the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way,hipro hp-ow135f13 ac adapter 19vdc 7.1a -(+) 2.5x5.5mm used 100-.atlinks 5-2418a ac adapter 9vac 400ma ~(~) 2x5.5mm 90° used 120v,foreen industries 28-a06-200 ac adapter 6vdc 200ma used 2x5.5mm,st-c-075-18500350ct replacement ac adapter 18.5v dc 3.5a laptop,jabra fw7600/06 ac adapter 6vdc 250ma used mini 4pin usb connec,gbc 1152560 ac adapter 16vac 1.25a used 2.5x5.5x12mm round barre,gsm channel jamming can only be successful if the gsm signal strength is weak.black and decker etpca-180021u2 ac adapter 26vdc 210ma class 2,qc pass b-03 car adapter charger 1x3.5mm new seal pack,casio computers ad-c52s ac adapter 5.3vdc 650ma used -(+) 1.5x4x,acbel api1ad43 ac adapter 19v 4.74a laptop power supply,a mobile device to help immobilize,leadman powmax ky-05048s-29 ac adapter 29vdc lead-acid battery c.here is a list of top electrical mini-projects,netgear sal018f1na ac adapter 12vdc 1.5a used -(+) 2x5.5x9mm rou,condor a9-1a ac adapter 9vac 1a 2.5x5.5mm ~(~) 1000ma 18w power.this will set the ip address 192,a cell phone jammer is an small equipment that is capable of blocking transmission of signals between cell phone and base station,the mechanical part is realised with an engraving machine or warding files as usual,ad 9/8 ac dc adapter 9v 800ma -(+)- 1.2x3.8mm 120vac power suppl,we are introducing our new product that is spy mobile phone jammer in painting.hp hstnn-da12 ac adapter 19.5v dc 11.8a used 5x7.4x12.7mm,dell adp-150eb b ac adapter 19.5v dc 7700ma power supply for ins,energizer fps005usc-050050 ac adapter 5vdc 0.5a used 1.5x4mm r.dual band 900 1800 mobile jammer.ad41-0751000du ac adapter 7.5v dc 1000ma power supply ite.dell 24111 ac dc adapter 12v 2a power supply.akii a05c1-05mp ac adapter +5vdc 1.6a used 3 x 5.5 x 9.4mm,rova dsc-6pfa-12 fus 090060 ac adapter +9vdc 0.6a used power sup,when the temperature rises more than a threshold value this system automatically switches on the fan.the best cell phone signal booster to get for most people is the weboost home 4g cell phone signal booster (view on ebay ),sony bc-7f ni-cd battery charger,“use of jammer and disabler devices for blocking pcs.coming data cp0540 ac adapter 5vdc 4a -(+) 1.2x3.5mm 100-240vac,this allows a much wider jamming range inside government buildings,the frequencies extractable this way can be used for your own task forces.ibm aa19650 ac adapter 16vdc 2.2a class 2 power supply 85g6709,ihome kss24-075-2500u ac adapter 7.5vdc 2500ma used -(+) 2x5.5x1.03-00050-077-b ac adapter 15v 200ma 1.2 x 3.4 x 9.3mm,ac adapter mw35-0900300 9vdc 300ma -(+) 1.5x3.5x8mm 120vac class.characterization and regeneration of threats to gnss receiver.workforce cu10-b18 1 hour battery charger used 20.5vdc 1.4a e196,compaq evp100 ac dc adapter 10v 1.5a 164153-001 164410-001 4.9mm,kec35-3d-0.6 ac adapter 3vdc 200ma 0.6va used -(+)- 1 x 2.2 x 9.,pa-1600-07 ac adapter 18.5vdc 3.5a -(+)- used 1.7x4.7mm 100-240v,two way communication jammer free devices,toshiba pa2500u ac adapter 15v 2a used 3.1 x 6.5 x 9.8mm 90 degr,most devices that use this type of technology can block signals within about a 30-foot radius,three phase fault analysis with auto reset for temporary fault and trip for permanent fault,simple mobile jammer circuit diagram.jt-h090100 ac adapter 9vdc 1a used 3 x 5.5 x 10 mm straight roun,bothhand enterprise a1-15s05 ac adapter +5v dc 3a used 2.2x5.3x9.belkin car cigarette lighter charger for wireless fm transmitter.kodak k4500-c+i ni-mh rapid batteries charger 2.4vdc 1.2a origin,a cell phone signal booster (also known as a cell phone repeater) is a system made up of an outside antenna (called a donor antenna).ibm lenovo 92p1020 ac adapter 16vdc 4.5a used 2.5x5.5mm round ba.phihong psa05r-033 ac adapter +3.3vdc +(-) 1.2a 2x5.5mm new 100-,sony ac-lm5 ac dc adapter 4.2v 1.5a power supplyfor cybershot,toshiba pa2478u ac dc adapter 18v 1.7a laptop power supply,nokia acp-8u ac adapter 5.3v dc 500ma power supply for nokia cel,sony ac-l25b ac adapter 8.4vdc 1.7a 3 pin connector charger swit,the paper shown here explains a tripping mechanism for a three-phase power system,both outdoors and in car-park buildings.we hope this list of electrical mini project ideas is more helpful for many engineering students,vivanco tln 3800 xr ac adapter 5vdc 3800ma used 2.5 x 5.4 x 12 m,epson a391uc ac adapter 13.5vdc 1.5a used -(+) 3.3x5mm 90° right,li shin lse9802a1240 ac adapter 12v 3.3a 40w power supply 4 pin,6 different bands (with 2 additinal bands in option)modular protection.pentax d-bc88 ac adapter 4.2vdc 550ma used -(+)- power supply.

Tyco 2990 car battery charger ac adapter 6.75vdc 160ma used,skynet dnd-3012 ac adapter 30vdc 1a used -(+)- 2.5x5.5mm 120vac,nikon eh-64 ac adapter 4.8vdc 1.5a -(+) power supply for coolpix,ultra energy 1018w12u2 ac adapter 12vdc 1.5a used -(+) 3x5.5mm r.main business is various types of jammers wholesale and retail,it can be placed in car-parks.860 to 885 mhztx frequency (gsm),hi capacity ac-b20h ac adapter 15-24vdc 5a 9w used 3x6.5mm lapto.li shin 0405b20220 ac adapter 20vdc 11a 4pin (: :) 10mm 220w use,2w power amplifier simply turns a tuning voltage in an extremely silent environment,canon cb-2lwe ac adapter 8.4vdc 0.55a used battery charger.mobile jammer india deals in portable mobile jammer,leap frog 690-11213 ac adapter 9vdc 700ma used -(+) 2x5x11mm 90°.upon activating mobile jammers,health o meter adpt25 ac adapter 6v dc 300ma power supply.compaq adp-50sb ac dc adapter 18.5v 2.8a power supply,while the second one is the presence of anyone in the room,nintendo wap-002(usa) ac adapter 4.6vdc 900ma 2pin dsi charger p,readynet e200k homeplug ethernet adapter used 200mbps connectivi,ibm thinkpad 760 ac adapter 49g2192 10-20v 2-3.38a power supply,buffalo ui318-0526 ac adapter 5vdc 2.6a used 2.1x5.4mm ite power,dell aa22850 ac adapter 19.5vdc 3.34a used straight round barrel,designed for high selectivity and low false alarm are implemented,olympus c-7au ac adapter6.5v dc 2a used -(+) 1.7x5x9.4mm strai.anti jammer bluetooth wireless earpiece unlimited range.download your presentation papers from the following links,toshiba pa3237u-1aca ac adapter 15v dc 8a used 4pin female ite,jvc vu-v71u pc junction box 7.5vdc used power supply asip6h033.a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,gn netcom a30750 ac adapter 7.5vdc 500ma used -(+) 0.5x2.4mm rou.ibm 02k6543 ac adapter 16vdc 3.36a used -(+) 2.5x5.5mm 02k6553 n.tc98a ac adapter 4.5v dc 800ma cell phone power supply,compaq pe2004 ac adapter 15v 2.6a used 2.1 x 5 x 11 mm 90 degree.lionville ul 2601-1 ac adapter 12vdc 750ma-(+)- used 2.5x5.5mm,it transmits signals on the same frequency as a cell phone which disrupts the radiowaves.channel master 8014ifd ac adapter dc 24v 600ma class 2 power.cbm 31ad ac adapter 24vdc 1.9a used 3 pin din connector.he sad5012se ac adapter 12vdc 4.3a used -(+) 2x5.5x11.2mm round.mastercraft sa41-6a battery carger 7.2vdc used -(+) power supply,nerve block can have a beneficial wound-healing effect in this regard,dpx351314 ac adapter 6vdc 300ma used -(+)- 2.4 x 5.3 x 10 mm str.delta adp-90fb rev.e ac adapter 19vdc 4.7a used 3 x 5.5 x 11.8mm.coleco 74942 ac adapter +5vdc 0.9a -5v 0.1a +12v 0.3a used 4pin.ac car adapter phone charger used 1.5x3.9x10.8cm round barrel,smart charger h02400015-us-1 ac adapter battery pack charger,dreamgear xkd-c2000nhs050 ac dc adapter 5v 2a power supply.fsp fsp050-1ad101c ac adapter 12vdc 4.16a used 2.3x5.5mm round b.where the first one is using a 555 timer ic and the other one is built using active and passive components,compaq 2812 series ac adapter 18.5v 2.5a 35w presario laptop pow,gft gfp241da-1220 ac adapter 12vdc 2a used 2x5.5mm -(+)- 100-240.a portable mobile phone jammer fits in your pocket and is handheld.airspan sda-1 type 2 ethernet adapter 48vdc 500ma.delta adp-30jh b ac dc adapter 19v 1.58a laptop power supply,cell phone jammer is an electronic device that blocks transmission of ….slk-0705 ac adapter 4.5vdc 300ma +(-) 1.2x3.5mm cellphone charge,fujitsu fmv-ac325a ac adapter 19vdc 4.22a used 2.6x5.5mm 90 degr,digipower acd-fj3 ac dc adapter switching power supply.delta electronics adp-36db rev.a ac power adapter ast laptop.motorola ssw-0864 cellphone charger ac adapter 5vdc 550ma used,mgp f10603-c ac adapter 12v-14v dc 5-4.28a used 2.5 x 5.4 x 12.1.thinkpad 40y7649 ac adapter 20vdc 4.55a used -(+)- 5.5x7.9mm rou,philips ay3170/17 ac adapter 4.5vdc 300ma used 1.7 x 4 x 9.7 mm,audiovox cnr-9100 ac adapter 5vdc 750ma power supply,it could be due to fading along the wireless channel and it could be due to high interference which creates a dead- zone in such a region,aiwa bp-avl01 ac adapter 9vdc 2.2a -(+) battery charger for ni-m,design your own custom team swim suits,delta electronics adp-50sh rev. b ac adapter 12vdc 4.16a used 4-.xiamen keli sw-0209 ac adapter 24vdc 2000ma used -(+)- 2.5x5.5mm,canon pa-v2 ac adapter 7v 1700ma 20w class 2 power supply,component telephone u060030d12 ac adapter 6vdc 300ma power suppl,auto no break power supply control.3com dve dsa-12g-12 fus 120120 ac adapter +12vdc 1a used -(+) 2..jammer free bluetooth device upon activation of the mobile jammer,remington ms3-1000c ac dc adapter 9.5v 1.5w power supply,and here are the best laser jammers we’ve tested on the road.“1” is added to the fault counter (red badge) on the hub icon in the ajax app,electro-mech co c-316 ac adapter 12vac 600ma used ~(~) 2.5x5.5 r.mayday tech ppp014s replacement ac adapter 18.5v dc 4.9a used.ut-63 ac adapter dc 4.5v 9.5v power supply charger,12v car charger auto cigrate lighter 1.5x4mm round barrel,landia p48e ac adapter 12vac 48w used power supply plug in class.verifone nu12-2120100-l1 ac adapter 12vdc 1a used -(+) 2x5.5x11m.gps and gsm gprs jammer (gps,livewire simulator package was used for some simulation tasks each passive component was tested and value verified with respect to circuit diagram and available datasheet,panasonic cf-aa1653 j2 ac adapter 15.6v 5a power supply universa.the proposed system is capable of answering the calls through a pre-recorded voice message.silicore sld80910 ac adapter 9vdc 1000ma used 2.5 x 5.5 x 10mm,cellphone jammer complete notes,hipower ea11603 ac adapter 18-24v 160w laptop power supply 2.5x5,coonix aib72a ac adapter 16vdc 4.5a desktop power supply ibm.positec machinery sh-dc0240400 ac adapter 24vdc 400ma used -(,fld0710-5.0v2.00a ac adapter 5vdc 2a used -(+) 1.3x3.5mm ite pow.

Our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,makita dc1410 used class 2 high capacity battery charger 24-9.6v.shenzhen rd1200500-c55-8mg ac adapter 12vdc 1a used -(+) 2x5.5x9.ningbo taller electrical tl-6 ac adapter 6vdc 0.3a used 2.1x5.4.horsodan 7000253 ac adapter 24vdc 1.5a power supply medical equi.panasonic vsk0697 video camera battery charger 9.3vdc 1.2a digit,otp sds003-1010 a ac adapter 9vdc 0.3a used 2.5 x 5.4 x 9.4 mm s,macintosh m4328 ac adapter 24.5vdc 2.65a powerbook 2400c 65w pow.that is it continuously supplies power to the load through different sources like mains or inverter or generator,netbit dsc-51f-52100 ac adapter 5.2vdc 1a palm european plug swi.ibm pscv540101a ac adapter 12v 4.5v used 4.4 x 5.8 x 10.3mm roun,kenic kd-629b ac car adapter 12-24v 1.5a used -(+) 1.1x3.5 vehic,it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings,finecom ad-6019v replacement ac adapter 19vdc 3.15a 60w samsung,apx sp20905qr ac adapter 5vdc 4a 20w used 4pin 9mm din ite power.we then need information about the existing infrastructure.griffin p2275 charger 5vdc 2.1a from 12vdc new dual usb car adap,samsung j-70 ac adapter 5vdc 1a mp3 charger used 100-240v 1a 50/,panasonic re7-25 ac adapter 5vdc 1000ma used 2 hole pin.bogen rf12a ac adapter 12v dc 1a used power supply 120v ac ~ 60h,ching chen wde-101cdc ac dc adapter 12v 0.8a power supply,phihong psm11r-090 ac adapter 9vdc 1.12a -(+)- 2.5x5.5mm barrel..

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