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Part 1 of a Two-Part Story. Read Part 2 here. Cover: GPS World By Bradford W. Parkinson and Stephen T. Powers, with Gaylord Green, Hugo Fruehauf, Brock Strom, Steve Gilbert, Walt Melton, Bill Huston, Ed Martin, James Spilker, Fran Natali, Joe Strada, Burt Glazer, Dick Schwartz, Tom Stansell, and others The original system study, the key innovations, and the forgotten heroes of the world’s first — and still greatest — global navigation satellite system. True history, told by the people who made it. Part One of a Two-Part Special Feature. The stealth utility: over the past 30 years, a new entity has steadily and stealthily crept into the fabric of worldwide society, creating capabilities and dependencies that did not exist before. This utility is known as the Global Positioning System, or GPS. With more than a billion GPS receivers in use, this stunning achievement has truly revolutionized the way the world functions in the 21st century. Virtually every cell-phone system relies on GPS for timing. Almost every ship and aircraft carries multiple GPS receivers to provide positioning information. Other applications span military targeting, transportation, object tracking, and resource identification. Today, the loss of GPS signals would have catastrophic consequences. How did GPS come into being? What technologies were essential to its success? Who developed those technologies? Recently a number of GPS histories have appeared that are very inaccurate on these subjects. Our purpose in writing this account is to set the record straight, and in so doing to give credit to many of the original developers of GPS whose contributions have somehow been forgotten. Throughout this article you will find their names highlighted. Space does not permit us to name the many other individuals who deserve enormous credit for the subsequent refinement and invention of new GPS applications. Figure 1 gives a summary view of the history of U.S. satellite-based navigation, particularly GPS. Details of the Russian GLONASS and the European Galileo systems are not included as they arrived later, and generally mimicked the GPS development albeit with their own, locally developed detailed designs. Figure 1. The eras of satellite navigation. (Credit: Bradford W. Parkinson and Stephen T. Powers) Dr. Richard Kershner, who led the development of Transit. On his left, young Col. Bradford Parkinson, who led the development of GPS. (Credit: Bradford W. Parkinson and Stephen T. Powers) This history focuses on the period up to about 1980, when GPS was approved for full-scale development. Between that time and the date that GPS was declared fully operational, April 27, 1995, many additional contributions were made. The system withstood several early attempts by the Air Force to cancel it entirely. Fortunately, those attempts did not succeed, and the Air Force now fully embraces GPS as an essential part of virtually every weapon system in the inventory. We call this a tribute to the almost-forgotten people whose intellectual labor and skill initially developed GPS. As we unveil this story, we will point out the original — and critical — system study, the 1966 Woodford/Nakamura Report, that became the essential blueprint for GPS. Many people are unaware of this study since, in its original form, it was classified U.S. Department of Defense (DoD) Secret. It was not declassified until August 1979, more than a year after the first launch of a GPS operational satellite in February 1978. We also intend to describe and justify the key innovation that enabled the system. This keystone technology is the GPS code-division multiple-access (CDMA) signal. While CDMA was necessary for GPS success, it was by no means sufficient. We will also define and describe the five major original challenges that had to be met to achieve the success that GPS now enjoys; that will come in the second installment of this history, to appear in next month’s issue. Mathematician Bill Guier (l) and physicist George Weiffenbach (r), told APL Research Center director Frank T. McClure (c), about their success using Doppler tracking for satellites. “McClure’s brain started going into fast forward,” remembered John Dassoulas. “Knowing the navigational challenges the U.S. Navy faced, McClure said, ‘Well, if you can find out where the satellite is, you ought to be able to turn that problem upside down and find out where you are.’” (Credit: Bradford W. Parkinson and Stephen T. Powers) GPS Predecessors: Transit On October 4, 1957, the entire world was amazed by the launch of Russia’s Sputnik satellite. The American public greeted this event with both apprehension and curiosity. Both the Army and Navy had been quietly working on satellite projects for some years. In an attempt to catch up, the United States had a spectacular failed launch when the Naval Research Laboratory’s (NRL’s) TV-3 crashed on December 6, 1957. On January 31, 1958, the United States Army launched a grapefruit-sized satellite, Explorer 1. The NRL then achieved success with the launch of TV-4, renamed Vanguard-1, on March 27, 1958. In 1958, the Applied Physics Laboratory (APL) of Johns Hopkins University employed an extremely competent team of engineers and scientists. Two of those scientists, Drs. William Guier and George Weiffenbach, began to study the orbits of the new Sputnik satellites. The satellites were broadcasting a continuous tone signal. Their velocity relative to the ground created a Doppler shift of that signal that was unique. After some innovative work, Guier and Weiffenbach discovered they could determine the Sputnik’s orbit with a single pass of the vehicle. At that point Frank McClure of APL made a very creative suggestion: Why not turn the problem upside down? Using a known satellite position, a navigator could determine his location anywhere in the world after receiving and processing the satellite signal for 15 minutes. His insight became the basis for the Navy’s Transit satellite program, also known as the Navy Navigation Satellite System (Figure 2). This pioneering system was developed under the leadership of Dr. Dick Kershner, head of the Space Department of APL. Transit’s main purpose was to provide position updates to the United States submarine ballistic-missile force then under development. These submarines were a major deterrent during the Cold War. Transit was first tested in 1960, and by 1964 the system was fully operational. Under Kershner, APL rapidly mastered the art of building long-life satellites. In fact, two of the vehicles continued operation for more than 20 years. Figure 2. The Transit birdcage of operational orbits. (Credit: Bradford W. Parkinson and Stephen T. Powers) Transit was a relatively small satellite that initially used solar power and gravity-gradient stabilization (Figure 3). It provided a position fix every few hours; fixes took 10 to 16 minutes of exposure of the submarine’s antenna on the surface. It achieved 25-meter accuracy, but only in two dimensions. Further, if the user was moving, accurate velocity measurement was critical: a 1-knot error would produce a 0.2-nautical mile position error. All Navy ships could use the system, and in 1967 Transit was offered to the civilian community by Vice President Hubert Humphrey. Magnavox became the principal developer of civil user sets with Tom Stansell as an early expert in the technology. Contributions to GPS. The Transit program developed a technique essential for GPS: the use of two frequencies to calibrate the time delay of the radio signal induced by the ionosphere. This dual-frequency technique was incorporated into GPS to attain the highest positioning accuracy. In addition, Transit also pio neered the accurate prediction of satellite orbits, another essential GPS technology. Orbit prediction will be highlighted later, as one of the five fundamental challenges that faced GPS system designers. In 1974, Transit made a further contribution to GPS development that we discuss in that approximate timeframe. Figure 3. A Transit satellite showing the gravity-gradient boom that kept the antennas pointing at the earth. (Credit: Bradford W. Parkinson and Stephen T. Powers): Program 621B As early as 1962, Dr. Ivan Getting, president of the Aerospace Corporation, saw the need for a new satellite-based navigation system. He envisioned a more accurate positioning system that would be available in three dimensions, 24 hours a day, seven days a week. He had direct access to the highest levels of the Pentagon and was a tireless advocate for his vision. Getting’s energy and foresight in the early 1960s were essential to gaining Air Force support to study system alternatives. As a result, the Air Force formed a new satellite navigation program that was later named 621B. Getting’s efforts were recognized in 2002 when he shared the Charles Stark Draper Prize of the National Academy of Engineering with Bradford Parkinson. By 1962, engineers at Aerospace, under Air Force sponsorship, were heavily immersed in studying the system aspects of a new navigational satellite system. From 1964 to 1966, Aerospace carried out an extensive, formal system study whose principal authors were James Woodford and Hideyoshi Nakamura, both highly regarded space-systems engineers. Their work was summarized as a DoD secret briefing in August 1966. As a result of the classification, it was unavailable to anyone outside the project until 13 years later, in 1979, when it was finally declassified (figure 4). The Woodford/Nakamura Report was a complete system study that examined these issues: capabilities and limitations of then-current DoD navigation systems; tactical applications and utility of improved positioning accuracy; comprehensive analysis of alternative system configurations and techniques for positioning, using satellites. The report concluded with a set of recommendations for advanced technology development for navigation satellite programs. Figure 4. Front page of the seminal GPS system study performed from 1964 to 1966 by USAF 621B Program. Originally classified secret, it was not declassified until after the initial GPS satellite had been launched. This was the essential foundation to the GPS System design. (Credit: Bradford W. Parkinson and Stephen T. Powers) The detailed analysis of possible passive navigation techniques was extremely important. It pointed out that the most capable passive-ranging design, called triple delta rho, would eliminate the need for an extremely stable clock in the user equipment and would provide three-dimensional positioning. (In this article we use clock, oscillator, and frequency standard interchangeably. The timing community makes some distinctions among these words, but for purposes of this history the distinctions are not particularly important.) This later was selected as the fundamental GPS system concept of ranging to four satellites simultaneously. Key conclusions of the 1966 study advocated: passive ranging from the satellites (the issue was which ranging signal to use) atomic clocks in space, and a technology program to develop space hardened atomic clocks further system studies as well as experimental demonstrations. Since the full survey of alternative system configurations was extremely important in selecting an optimum system configuration, we reproduce the summary in figure 5. Note that the “Computation Performed by User” is split into two columns. Focus on the columns of the one-way passive ranging techniques with the red outline. Inside, there are two “user boxes,” one with A and one with X. The A shows the user needs an atomic clock. The X shows the user needs only a crystal clock. The option later selected for GPS is designated as G. This technique is the 3Δρ (triple delta rho, or four satellites) that eliminated the need for the user atomic clock, and provided three-dimensional positioning (really four-dimensional since it also captured time). In October 1970, more than four years after the completion of this study, Roger Easton of NRL applied for a patent on the two-satellite, ρ-ρ technique (option N) that required an atomic clock for the user and was only two-dimensional. The patent (U.S. 3,789,409) was granted in 1974, a year after the three-dimensional design of the GPS system had already been defined in the Lonely Halls Pentagon meeting to be described later. Figure 5. Summary of the alternative satellite-based navigation techniques from the1964–66 USAF/621B study. The most capable option, circled in green, became the basis for the White Sands prototyping and testing, and then evolved into GPS. NRL applied for a patent on the less capable technique (red line) four years after the Woodford/Nakamura Study was completed. (Credit: Bradford W. Parkinson and Stephen T. Powers) Credit: Bradford W. Parkinson and Stephen T. Powers   More 621B Studies. From 1966 to 1972, program 621B continued with trade-off studies including: signal modulation, user data processing techniques, orbital configuration, orbital prediction, receiver accuracy, error analysis, system cost, and comprehensive estimates of the tactical mission benefits. More than 90 reports completed by USAF/Aerospace during this period remain available in the Aerospace Corporation library. PRN or CDMA Signal Structure. Of these studies, the most important were those aimed at selecting the best passive ranging technique for the navigation signal. By 1967, it appeared that the best technique was a variation of a new communications modulation known as CDMA. Pioneering this signal were several outstanding scientists, Dr. Fran Natali and Dr. Jim Spilker (both of Philco-Ford), and Dr. Charlie Cahn (of Magnavox). Credit: Bradford W. Parkinson and Stephen T. Powers   This signal has many names. In addition to CDMA, it is sometimes called spread spectrum, since the energy of the signal was spread over a wide range of radio frequencies. It is also sometimes called PRN or pseudorandom noise because the encoded (and repeated) sequence appears to be random transitions of +1 and -1. The name code-division is used because each satellite is assigned its own coded signal. Each was a binary (digital) sequence selected to be uncorrelated with other signals and also uncorrelated with time shifts of the signal itself. The expected, powerful advantage of this technique was that all satellites would broadcast on exactly the same frequency. It would clearly lend itself to digital signal processing. Furthermore, and very important, any time-shifts induced by the receiver for the various satellite signals would be effectively eliminated. However, several significant questions concerning CDMA still needed resolution. These included: Could such a signal be easily acquired in the face of time uncertainty and Doppler shifts? Was there a technique to encrypt the military signal so that unauthorized users could not gain access? How would the c odes be easily selected to avoid a false lock and also allow additional satellites to be added without interfering with existing satellite signals? Would the anticipated complexity of the receiver drive costs to unacceptable levels? Was the signal resistant to accidental or deliberate interference? Could this signal accommodate communication capability for satellite location, satellite clock correction, and other parameters? Fortunately, in 1967 a technique for selecting orthogonal codes was invented by an accomplished applied mathematician, Dr. Robert Gold of the Magnavox Corp. Naturally these are now known as the Gold codes. His solution resolved the third CDMA issue stated above. White Sands Tests. To address the remaining issues, the 621B program developed two prototype versions of CDMA navigation receivers (Magnavox and Hazeltine) for testing at the White Sands Missile Range (WSMR). For these initial 1971 tests, 621B arranged four transmitters in a configuration known as the inverted range. (Interestingly, the more capable receiver was the MX-450 that was only on loan from Magnavox.) These transmitters broadcast CDMA signals from locations that were similar to a satellite configuration except that they were broadcast from the ground. For the simulation of satellite geometry, a balloon-based transmitter was also included for the aircraft-landing tests. Al Gillogly of Aerospace spent many hours installing and troubleshooting the test configuration. Al Gillogly, Aerospace engineer (left), setting up the critical tests of prototype GPS receivers at WSMR in 1970. (Credit: Bradford W. Parkinson and Stephen T. Powers) By 1972, program 621B had successfully proven the effectiveness and accuracy of the CDMA signal by demonstrating that such a configuration would achieve 5-meter, 3-dimensional navigation accuracy. Much credit for the painstaking analysis of these results should go to Bill Fees of Aerospace who wrote the final detailed test report. These test results answered most of the remaining issues regarding the CDMA signal. The tests also confirmed the power of the modulated signal by showing that all satellite signals could, indeed, be received simultaneously on the same frequency. These tests also corroborated the expectation that ranging to four satellites eliminated the need for a highly precise user atomic clock, while still supporting full, three-dimensional navigation. This became an extremely important feature of GPS. If each user had required an atomic-clock class frequency-standard, no inexpensive user equipment could have been produced within the technology horizon visible at that time. This is still true today. All this evidence supported CDMA as the passive ranging signal of choice and was available to the Air Force’s 621B team when the system configuration was selected at the September 1973 Pentagon meeting that will be discussed later. 621B Demo, Operational Differences. From the time of the 1966 Woodford/Nakamura study on, the Air Force and Aerospace advocated the use of atomic clocks in the operational satellites with the modulation also originating in the satellites. There were two significant risks to placing atomic clocks in the satellites: First, the technology readiness risk: no hardened atomic clocks had yet been designed and flown; and second, the political/budgeting risk associated with gaining approval for a development/demonstration program for the full capability. The Air Force developed a plan to reduce both risks. In late 1968, the Air Force’s NavSat program in the Plans Office (XR) at the Space and Missile Systems Organization (SAMSO) was redesignated as 621B. All of the various proposals that went forward from SAMSO to Headquarters came henceforth from the 621B office in XR. This included a proposal in early 1972 to deploy a four-satellite demonstration system. This proposal addressed both risks. It would reduce the technology readiness risk in the clocks by launching simple L-band transponders. At the same time, it would save substantial money, thereby reducing the political/budgeting risk. QZSS (Credit: Bradford W. Parkinson and Stephen T. Powers) In many circles, this proposal was erroneously thought of as 621B because it came from that office, but in fact, the operational concept for 621B never contemplated or advocated using transponders in the final operational system. Transponders had been rejected for the operational system because they could be easily jammed from the ground. Such a jamming signal would overpower the transponder and steal all of the transmitted energy away from the transponded navigational signal. This enemy jamming would shut down the entire system, clearly an unacceptable risk. Proposed Initial Constellation. To demonstrate four-satellite, passive ranging capability, 621B had studied a number of orbital configurations, including geo-synchronous and lower inclined orbits. The program proposed to place a constellation of three or four synchronous satellites in orbits over the United States. This array would allow extended periods of four-satellite testing without committing to a full global employment. If this demonstration were successful, the next step would have been to add three more longitudinal sectors, each with its own array. Again, the principal redeeming feature of this approach was that there was some hope of it being funded. The Air Force in the Pentagon placed enormous pressure on the 621B program to come up with the absolutely cheapest way to demonstrate the four-satellite approach. This proposed constellation design was a reasonable compromise, given the boundary conditions of a four-satellite demonstration and absolutely minimal cost. It is interesting that the Japanese, with a requirement to supplement GPS with satellite signals to improve coverage in urban areas (where there are high shading angles), have designed a very similar constellation. The Japanese configuration is intended to improve coverage restricted to their longitudinal sector of the globe. The new system is called Quasi-Zenith Satellite System (QZSS), and the Japanese appear to be well on the way to fielding it. Timation and NRL In 1964, the U.S. Navy initiated a second satellite program, named Timation, under the direction of Roger L. Easton, Sr., a long-time member of the NRL staff. The NRL’s Timation project was aimed at exploring techniques for passive ranging to satellites, as well as time transfer between various timing centers around the world. This project ran parallel to, and was in competition with, the Air Force Program. It subsequently developed a number of experimental satellites, the first of which was called Timation 1. This small satellite, weighing 85 pounds and producing 6 watts of power, was launched on May 27, 1967. Timation 1, developed by NRL, was a miniaturized, innovative design. The quartz clock was less stable than expected, apparently due to temperature and cosmic-ray effects. (Credit: Bradford W. Parkinson and Stephen T. Powers) The key feature of Timation 1 was that it included a very stable quartz clock. The fundamental ranging technique was to synchronize a clock at the user’s location with the clock on the satellite and use a passive-ranging signal structure called side-tone ranging. By 1968, NRL demonstrated single-satellite position fixes, accurate to about 0.3 nautical miles, that required about 15 minutes of data collection (Global Positioning System, Volume 1, chapter “Navigation Technology Program,” R.L. Easton, p.16). NRL engineers encountered two significant problems during their testing: sol ar radiation caused shifts in the clock’s frequency, and ionospheric group delay created ranging errors. The NRL launched a second satellite, Timation 2, into a 500-mile orbit on September 30, 1969. To calibrate ionospheric group delay, the satellite broadcast on two frequencies very similar to the technique pioneered by the Transit program. Its quartz oscillator was expected to be somewhat more stable, about one part in 1011. Again, a large frequency shift was observed in the clocks that was finally traced to a solar proton storm. NRL was able to demonstrate ranging accuracies of approximately 200 feet to a fixed location. Timation NTS-1. The last satellite in the original Timation series was launched in July 1974. By that time the Timation program had been placed under the GPS Joint Program Office in Los Angeles, reporting through the Navy Deputy, Cdr. Bill Huston, to the Program Director Col. Bradford Parkinson. The JPO had renamed the satellite as Navigation Technology Satellite (NTS-1). The gross weight had been increased to 650 pounds with a power requirement of 125 watts. This satellite, developed by Pete Wilhelm of NRL, was placed at an orbital altitude of 7,500 nautical miles. Timation NTS-1 carried two slightly modified commercial rubidium clocks. Unfortunately, attitude-stabilization problems induced temperature variations that masked any quantitative performance evalulation. The atomic clocks were not useful as prototypes for GPS. (Credit: Bradford W. Parkinson and Stephen T. Powers) The NTS satellites were strictly technology-testing satellites. For many reasons, they had no role in the development of the operational satellites by the JPO and Rockwell. The latter were operational satellites and were called NDS, for Navigation Development Satellites. They were the only ones used in the operational testing during phase I of GPS. NTS-1 included two small, lightweight rubidium oscillators as clocks. A German commercial company called Efratom had independently developed these models. Amazing at the time, they only consumed about 13 watts of power and weighed some four pounds each. Further Efratom involvement will be pointed out later. While NRL made some electronic modifications, the modified clocks were not in any sense able to withstand the radiation of the GPS orbits. The NTS-1 clocks were certainly not prototypes for the Rockwell clocks that were developed directly for the JPO and flown on the first block of GPS satellites. NRL tests showed that the modified rubidium clocks had an unacceptable level of sensitivity to temperature variations. Al Bartholemew of the NRL later wrote that “the lack of attitude stabilization system on NTS-1 resulted in large temperature variations which ultimately masked any quantitative evaluation of rubidium standard performance.” (Global Positioning System, volume 1, chapter “Satellite Frequency Standards,” C.A. Bartholomew, p. 25.) This apparently occurred because the satellite used a two-axis gravity gradient stabilization system that does not function well at these altitudes. The Navigation Development Satellites (NDS) satellites, later developed by the JPO, avoided this by developing a new, full three-axis, attitude-control system. NTS-1 carried other space technology demonstrations including highly efficient solar cells. Later, NRL developed a second (and last) satellite (NTS-II) for the GPS Program Office, after the Pentagon had approved the project in December 1973. The vehicle included two modified cesium beam oscillators developed by Frequency and Time Systems Inc. (FTS) of Danvers Massachusetts. The key atomic clock developer was the engineer and creative entrepreneur Robert Kern. This clock showed great initial promise but it was not yet a space prototype in terms of radiation hardening and parts life. In addition, the JPO provided a Rockwell-developed navigation payload for NTS-II that the JPO had developed for the operational GPS satellites. This would allow the NRL satellite to broadcast the GPS CDMA signal. Credit: Bradford W. Parkinson and Stephen T. Powers   NTS-II was launched on June 23, 1977, from Vandenberg Air Force Base. Originally it was hoped that NTS-II would be a part of the initial GPS test constellation. It could then have supplemented the satellites being developed by Rockwell, providing another passive ranging signal for the user equipment tests at Yuma Proving Ground. Unfortunately, the NRL ranging transmitter in NTS-II failed prior to the launch of the first JPO NDS satellites, rendering the NRL satellite unusable for the Yuma Proving Ground testing. “Of the two experimental cesium standards carried on NTS-II,” Ron Beard of NRL wrote, “one experienced a power supply failure after a period of satisfactory operation.” It is known that the other cesium clock continued to operate for over a year, but quantitative drift rates on orbit were never available. As a result of these failures, the cesium clock tests were inconclusive. (Proceedings of the IEEE 43rd Annual Symposium on Frequency Control, 1989, R.L. Beard, p. 276.) Only tests with the first four JPO/Rockwell satellites were available to support the full-scale development approval on June 5, 1979. For the next step, NRL defined a radiation-hardening program and contracted with FTS to develop a hardened cesium clock. This new clock was flown on the fourth operational GPS satellite (NDS 4, launched December 10, 1978). Unfortunately, the clock suffered a premature failure of the power supply after only 12 hours of operation. FTS soon found the root cause and fixed the design. Beginning with NDS 5, the on-board cesium clocks performed well and were equal or better in stability to the Rockwell rubidium oscillators. Competition, Lonely Halls By 1972, a few Pentagon authorities had recognized that a new satellite-based navigation system would be a valuable asset with multiple military applications. Literally hundreds of positioning and navigation systems in use by the DoD were expensive to maintain and upgrade. Obviously, a single replacement system offered significant cost savings. Unfortunately, the two competing concepts from 621B and NRL apparently confused the decision-makers. Discussions grew very acrimonious at times. As a result of this inter-service competition and a reluctance to commit the necessary monies, the Pentagon put off making any decision. In November of 1972, Col. Bradford Parkinson was the director of engineering for the Advanced Ballistic ReEntry Systems Program (ABRES) at SAMSO. Brig. Gen. Bill Dunn, who led the advance planning group (XR), identified Parkinson as a potential candidate to head the floundering 621B program. At Dunn’s behest, Lt. Gen. Kenneth Schultz, commander of SAMSO, asked Parkinson if he would like to be assigned to the 621B program. Parkinson had a very relevant background in navigation, guidance, and control that included a Ph.D. from Stanford in astronautical engineering. He had been chair of the Astronautics Department at the U.S. Air Force Academy, spent three years as a guidance analyst at the Central Inertial Guidance Test Facility, and was operationally oriented with 26 combat missions in AC-130 gunships. The background was a match, but Parkinson expressed an unwillingness to volunteer for the assignment if he were not assured that he would be the program director. Schultz said he could not yet make that promise. However, immediately after Parkinson left his office, the general reassigned him to the 621B program and effectively made him the director. Beginning in December, immediately after he assumed control of 621B, Parkinson instituted a series of 7 a.m. educational meetings. At these gatherings, the program staff reexamined every aspect of the proposed 621B program, including alternatives. This educational process was a key to having everyone in the Program Office completely understand the technical issues they faced. During this period Gen. Schultz supported the program in every way that he could. In particular, Parkinson was allowed to recruit Air Force officers whose background and experience were aligned with the needs of the fledgling program. All had advanced engineering degrees from the very best universities in the country including MIT, Michigan, and Stanford. In addition, virtually every officer had experience in developing real hardware or in testing inertial guidance systems. The first officer Parkinson brought aboard was Air Force Major Gaylord Green, who had worked for him on ABRES. Green’s creativity, focused on satellites and orbits, had an extremely important impact on the success of GPS. The result of Parkinson’s hunting license was a cadre of about 25 of the best and brightest people that the Air Force had to offer. In addition there was a small, carefully-selected group of Aerospace technical support personnel (led by Walt Melton from 1970 to 1972). This fine group of Aerospace engineers and scientists was experienced in an all technical aspects of space navigation programs and particularly skilled at issues relating to signal modulation, satellite position prediction, and building long-life satellites. Many of their names will be highlighted in Part Two of this story. The Aerospace contingent continued to enjoy the strong support of the president of the Aerospace Corporation, Ivan Getting. Replacing Melton early in Phase One was Ed Lassiter, who had extensive space-flight experience and was a mainstay of the early GPS development. Credit: Bradford W. Parkinson and Stephen T. Powers   During early spring of 1973, the director of Defense Research and Engineering (DDR&E), Dr. Malcolm Currie, formerly of Hughes Aircraft, who had just been appointed to the number three position in the DoD, found himself flying between Washington, D.C. and Los Angeles on most weekends. His secondary purpose was to oversee the relocation of his family, but he needed an official reason to travel to Los Angeles. So, each Friday afternoon he would visit SAMSO in Los Angeles for a presentation. After a few weeks, his host Gen. Schultz ran out of subjects to present, and instead invited Currie to spend an afternoon with his new program director, Col. Parkinson. Schultz’s invitation led to an astonishing meeting, because a newly-promoted colonel does not usually have the opportunity to confer with the number three person in the DoD over an uninterrupted three- or four-hour period. This informal meeting was held in private, in a very small cubicle within the JPO offices. With a Ph.D. in physics, Currie was a very quick study, so the interaction was lively and deep, delving into every aspect of the 621B proposal. After that meeting, Currie became a good friend to and a sponsor of the new satellite-based navigation program. He later played a critical role in ensuring DoD support, particularly in light of the Air Force’s attempts to cancel the infant program. DSARC 1. On August 17, 1973, Parkinson was invited to the Defense Systems Acquisition Review Council meeting to make a presentation on 621B. The meeting’s purpose was to determine whether to proceed with the concept demonstration program. It was held at the Pentagon, and attended by senior officers of all services, with Mal Currie presiding. At the meeting’s conclusion, the Council voted against approving the 621B program. Currie immediately invited Parkinson into his private office to tell him he wanted a new system proposal developed that would incorporate the best features of all the technical alternatives. He emphasized the need for a joint program involving all services. Lonely Halls Meeting. Parkinson immediately called a meeting in the Pentagon over Labor Day weekend, September 1973. Over that weekend, the world’s largest office building appeared to be a series of poorly-lit, uninhabited tunnels because everyone was away on vacation. The light at end of those tunnels, both figuratively and literally, came from a small conference room on the top floor, seating about a dozen attendees, all Air Force officers except for three Aerospace Corporation engineers. The purpose of the meeting was to define modifications to the 621B proposal that would meet Currie’s directive. Parkinson wanted the isolation to ensure unfettered creativity in defining the new proposal. Leading to this, the Analytical Sciences Corporation (TASC) under the guidance of Gaylord Green had completed a new systems study, a review and update of the earlier systems study directed by Jim Woodford and Hideyoshi Nakamura for project 621B in 1964–66. After much deliberation, over that weekend the JPO defined the GPS with ten facets: The fundamental 621B concept of simultaneous passive ranging to four satellites would be the underlying principle of the new system proposal, ensuring that user equipment would not require a synchronized atomic clock. The signal structure would be the 621B CDMA modulation. It would include both a clear, acquisition modulation (C/A) and a precision military modulation (P/Y). The C/A modulation was to be freely available to civil users throughout the world. There would be two GPS broadcast frequencies in the L band, using the same dual-frequency technique that Transit had employed to correct for ionospheric group delay, as well as providing redundancy. Based on the progress that NRL had made in satellite clocks, the program committed to space-hardened atomic clocks on the first operational/demonstration GPS satellites (called Navigation Development Satellites, or NDS). At the Lonely Halls meeting, Parkinson concluded that the NRL technology was relatively low-risk, obviating the need to use the ground-relay, experimental demonstration scheme that 621B had previously proposed. It later turned out that the clock development was not as mature as it appeared, but the JPO backup clock development by Rockwell was available in time for the first launch. The orbits for the satellites were to be inclined at 62º and not geosynchronous. Green proposed 11-hour, 58-minute (sidereal synchronous) orbits that gave about two hours of testing over the same United States test area each day. NRL had advocated similar 8- or 12-hour inclined orbits. Because of the need for an extensive testing program on an instrumented range, exact 8- or 12-hour orbits would have been unsatisfactory, because they would continuously shift relative to the Earth. While these orbits resembled those advocated by NRL, Green’s modification was critical to the success of the testing program. Orbit prediction would be handled with modifications to the Transit-developed orbit-prediction programs called Celeste. The initial test constellation would include four operational satellites, competitively procured, one of which would be a refurbished qualification model. They would be launched on refurbished Atlas-F rockets, which minimized cost, but also limited the number of solar panels that could be carried because of weight. A family of user equipment prototypes would be procured competitively. This equipment would span all normal military uses, and also include a low-cost set that would prototype civilian use. Where affordable, competitive contracts would be let. Particular attention would be devoted to user equipment integration with inertial navigation units and demonstration of anti-jam capabilities. The master control station and its backup would be on U.S. soil, but monitor stations would be placed around the world. > The testing would be principally performed at the Army’s Yuma test range with accuracy measured from a tri-lateration laser configuration. Using three laser ranging devices at the same time would ensure that all test vehicles could be measured to about a meter of positioning error. It was expected (and later proven) that this technique could even calibrate Air Force or Navy fighter aircraft flying close to Mach 1. Testing would make use of the inverted range concept, with satellites replacing each range transmitter as each newly launched GPS satellite became operational on orbit. Dual Use. One aspect should be strongly pointed out. Contrary to some versions of GPS history, from the very beginning, GPS was configured to be a dual-use system. Civilian users were to be given free access to the signal specification and were expected to use the so-called clear acquisition signal for navigation and other purposes. In fact, Parkinson highlighted civilian use when he testified before Congress on the proposed new system. GPS Approval. That Labor Day weekend of September 1973 had been a very busy three days. With help from the Air Staff Program Element Monitor (PEM) Lt. Col. Paul Martin, the Lonely Halls gathering developed a seven-page Decision Coordinating Paper (DCP) and a presentation of the new concept. Over the next two-and-a-half months there was a flurry of activity as Parkinson made presentations and defended the concept before all those who could block the proposal in the Pentagon. This effort was culminated with the approval to proceed on December 14, 1973. There were no significant modifications to the proposal that had been developed during the Lonely Halls meeting in the Pentagon. During the whole Phase I development, Parkinson resolved to avoid any conflict with the other original competitors to build a satellite-based navigation system. He deliberately ignored dubious claims of invention and statements regarding the origins of GPS technology. Until quite recently, he has overlooked these false claims by those who did not directly participate in determining the GPS architecture and did not participate in the specific GPS design and deployment. He felt the real purpose was to build the system, not to fight over credit. Recently an article appeared that implied that the GPS design was essentially the same as Timation. (“In what ways did GPS improve on Timation?” Easton: “I can’t think of any ways in which GPS improved on Timation. Essentially, they are the same system.” Interview in High Frontier magazine.) Aware that this incorrect statement denigrated the people who had first analyzed, advocated, and demonstrated the fundamental concept, as well as built the system, Parkinson resolved to correct the record, and highlight the names of those who deserve credit. This is a major purpose of this article. This article has been reviewed and approved for veracity by virtually all the key figures (still alive) who actually designed, built, and tested GPS. End of Part One. Watch for Part Two in our June issue. Some of the JPO Heroes at a Dining In. From left, Major Mel Birnbaum (made many important contributions. He was famous for marathon code reviews that could last 18 hours straight. He hated to miss schedules!); Col. Don Henderson (later Maj. Gen.), second Air Force Deputy; Major Ralph Tourino (later Maj. Gen.), Program Control; Lt. Col. Ken Juvette, director of procurement; and Lt. Cdr. Joe Strada, a key leader in the extensive test program. (Credit: Bradford W. Parkinson and Stephen T. Powers) Our Story Continues Part 2 of “The Origins of GPS” appears in the June 2010 issue of GPS World. GPS Phase I program approval meant that the real work could begin. By January 1974, the GPS program at the JPO was well underway. Of course there were many challenges, but Five Challenges, principally engineering, stand out as particularly daunting. Part Two also describes GPS’ most fundamental innovation, more on system origins, innovations of the Joint Program Office (see photo of key figures), and thoughts on the future of GPS and GNSS.

gps jammer in the us russia

Due to the high total output power.sony ac-l15b ac dc adapter 8.4v 1.5a power supply for camcorder,strength and location of the cellular base station or tower,kensington m01062 ac adapter 50w 12vdc 3a 19v 2.5a 5v 0.5a used,li shin 0405b20220ac adapter 20vdc 11a -(+) used 5x7.4mm tip i.bml 163 020 r1b type 4222-us ac adapter 12vdc 600ma power supply,hallo ch-02v ac adapter dc 12v 400ma class 2 power supply batter,artestyn ssl10-7660 ac dc adapter 91-58349 power supply 5v 2a,condor 3a-181db12 12v dc 1.5a -(+)- 2x5.4mm used ite switch-mode,cte 4c24040a charger ac adapter 24vdc 4a 96w used 3pin xlr power,elpac power fw6012 ac adapter 12v dc 5a power supply.ktec ksaa0500120w1us ac adapter 5vdc 1.2a new -(+)- 1.5x4mm swit.ridgid r86049 12vdc battery charger for drill impact driver cord,delta hp adp-15fb ac adapter 12v dc 1.25a power supply pin insid,duracell cef-20 nimh class 2 battery charger used 1.4vdc 280ma 1,kodak mpa7701l ac adapter 24vdc 1.8a easyshare dock printer 6000,solutions can also be found for this,lg lcap16a-a ac adapter 19vdc 1.7a used -(+) 5.5x8mm 90° round b.kodak k4500 ni-mh rapid battery charger2.4vdc 1.2a wall plug-i,hp f1279a ac adapter 12vdc 2.5a used -(+) 2x4.8mm straight,information technology s008cm0500100 ac adapter 5vdc 1000ma used,this project shows the automatic load-shedding process using a microcontroller,ap3911 ac dc adapter5v dc 500ma new +(-) 1.3x3.4x7.5mm straigh,hi capacity ea1050a-190 ac adapter 19vdc 3.16a used 5 x 6 x 11.dell adp-150eb b ac adapter19.5vdc 7700ma power supplyd274,by activating the pki 6050 jammer any incoming calls will be blocked and calls in progress will be cut off.lei nu30-4120250-i3 ac adapter 12vdc 2.5a used 2x5.5mm 30w motor.we only describe it as command code here.p-056a rfu adapter power supply for use with playstation brick d,extra shipping charges for international buyers partial s&h paym.ibm 02k6756 ac adapter 16vdc 4.5a 2.5x5.5mm -(+) 100-240vac powe,ultra ulac901224ap ac adapter 24vdc 5.5a used -(+)5.5x8mm power.complete infrastructures (gsm.cardio control sm-t13-04 ac adapter 12vdc 100ma used -(+)-,rs-485 for wired remote control rg-214 for rf cablepower supply.hp pavilion dv9000 ac dc adapter 19v 4.74a power supply notebook,although we must be aware of the fact that now a days lot of mobile phones which can easily negotiate the jammers effect are available and therefore advanced measures should be taken to jam such type of devices,dura micro pa-215 ac adapter 12v 1.8a 5v 1.5a dual voltage 4pins,toshiba adpv16 ac dc adapter 12v 3a power supply for dvd player.dewalt dw9107 one hour battery charger 7.2v-14.4v used 2.8amps.ibm 02k6808 ac adapter 16vdc 3.5a used 2.6x5.5x11mm straight,insignia u090070d30 ac adapter 9vdc 700ma used +(-)+ 2x5.5mm rou,ilan elec f1700c ac adapter 19v dc 2.6a used 2.7x5.4x10mm 90,a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible,energizer tsa9-050120wu ac adapter 5vdc 1.2a used -(+) 1x 3.5mm,apd da-30i12 ac adapter 12vdc 2.5a power supply for external hdd,accordingly the lights are switched on and off,sunfone acu034a-0512 ac adapter 12vc 5v 2a used 3 pin mini din a,braun 3 709 ac adapter dc 1.3w class 2 power supply plug in char,philips hs8000 series coolskin charging stand with adapter.jhs-e02ab02-w08a ac adapter 5v 12vdc 2a used 6pin din power supp.slk-0705 ac adapter 4.5vdc 300ma +(-) 1.2x3.5mm cellphone charge.here is the project showing radar that can detect the range of an object.

s-gps jammer 12v inline	6333	8794	1630
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jammer in engels theory	6813	3136	1126
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gps jammers sale by state insurance	6619	3397	6197
jamming signal ethernet to usbc	495	2640	1586
jammer gps opinie ball	8784	4885	8181

This provides cell specific information including information necessary for the ms to register atthe system,delta adp-150cb b ac adapter 19v 7.9a power supply,delta adp-15zb b ac adapter 12vdc 1.25a used -(+) 2.5x5.5x10mm r.rocket fish rf-bslac ac adapter 15-20vdc 5a used 5.5x8mm round b,jvc puj44141 vhs-c svc connecting jig moudule for camcorder,li shin lse9802a2060 ac adapter 20vdc 3a 60w used -(+) 2.1x5.5mm,aa41-120500 ac adapter 12vac 500ma used 1.9x5.5x12mm straight ro.mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means,audiovox ild35-090300 ac adapter 9v 300ma used 2x5.5x10mm -(+)-,produits de bombe jammer+433 -+868rc 315 mhz,ibm pscv 360107a ac adapter 24vdc 1.5a used 4pin 9mm mini din 10,altec lansing eudf+15050-2600 ac adapter 5vdc 2.6a -(+) used 2x5.finecom thx-005200kb ac adapter 5vdc 2a -(+)- 0.7x2.5mm switchin.mw mws2465w-1 ac adapter 15-24vdc 63w used straight round barrel.cell phone scanner jammer presentation.nexxtech 4302017 headset / handset switch.shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking,ottoman st-c-075-19000395ct ac adapter 19vdc 3.95a used3 x 5.4,cell phones are basically handled two way ratios.nec pa-1600-01 ac adapter 19v dc 3.16a used 2.8x5.5x10.7mm,2 w output power3g 2010 – 2170 mhz,while the second one is the presence of anyone in the room,hoover series 300 ac adapter 4.5vac 300ma used 2x5.5x11mm round,this blocker is very compact and can be easily hide in your pocket or bag,frequency counters measure the frequency of a signal.the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer,i adaptor ac adapter 24vdc 1.9a 2 century cia2/g3 i.t.e power su.handheld powerful 8 antennas selectable 2g 3g 4g worldwide phone jammer &.nokia acp-9u ac adapter 6.2v 720ma new 1.2 x 3.4 x 7.7mm round.fujitsu sec80n2-19.0 ac adapter 19vdc 3.16a used -(+)- 3x5.5mm 1.kvh’s new geo-fog 3d inertial navigation system (ins) continuously provides extremely accurate measurements that keep applications operating in challenging conditions.tec b-211-chg-qq ac adapter 8.4vdc 1.8a battery charger,ts-13w24v ac adapter 24vdc 0.541a used 2pin female class 2 power,110 to 240 vac / 5 amppower consumption,hand-held transmitters with a „rolling code“ can not be copied.ibm 07h0629 ac adapter 10vdc 1a used -(+)- 2 x 5 x 10 mm round b.cfaa41 dc adapter 15vdc 4ah car charger power supply switching f,johnlite 1947 ac adapter 7vdc 250ma 2x5.5mm -(+) used 120vac fla,ault 3com pw130 ac adapter 48vdc 420ma switching power supply,compaq evp100 ac dc adapter 10v 1.5a 164153-001 164410-001 4.9mm,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,when the temperature rises more than a threshold value this system automatically switches on the fan,cyber acoustics sy-09070 ac adapter 9vdc 700ma power supply,providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements,developed for use by the military and law enforcement,hi capacity san0902n01 ac adapter 15-20v 5a -(+)- 3x6.5mm used 9,sanyo var-s12 u ac adapter 10v 1.3a camcorder battery charger.du090060d ac adapter 9vdc 600ma class 2 power supply.cell phone jammer and phone jammer,casio ad-12ul ac adapter 12vdc 1500ma +(-) 1.5x5.5mm 90° 120vac,intertek 99118 fan & light control used 434mhz 1.a 300w capacito.jabra acw003b-05u ac adapter 5v 0.18a used mini usb cable supply.hipro hp-a0652r3b ac adapter 19v 3.42a used 1.5x5.5mm 90°round b.

Replacement pa-1700-02 ac adapter 19v 3.42a used,kodak mpa7701 ac adapter 24vdc 1.8a easyshare dock printer serie,liteon hp ppp009l ac adapter 18.5v dc 3.5a 65w power supply,pi ps5w-05v0025-01 ac adapter 5vdc 250ma used mini usb 5mm conne.comos comera power ajl-905 ac adapter 9vdc 500ma used -(+) 2x5.5,this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,datalogic powerscan 7000bt wireless base station +4 - 14vdc 8w.acbel ad9014 ac adapter 19vdc 3.42a used -(+)- 1.8x4.8x10mm.fujitsu fmv-ac325a ac adapter 19vdc 4.22a used 2.6x5.5mm 90 degr,kodak vp-09500084-000 ac adapter 36vdc 1.67a used -(+) 6x4.1mm r,dc90300a ac adapter dc 9v 300ma 6wclass 2 power transformer.520-ps12v2a medical power supply 12v 2.5a with awm e89980-a sunf.olympus bu-100 battery charger used 1.2v 490ma camedia 100-240v,ktec wem-5800 ac adapter 6vdc 400ma used -(+) 1x3.5x9mm round ba.police and the military often use them to limit destruct communications during hostage situations,oem dds0121-052150 5.2vdc 1.5a -(+)- auto cigarette lighter car,delta electronics adp-10mb rev b ac adapter 5v dc 2a used 1.8 x,ikea yh-u050-0600d ac adapter 5vdc 500ma used -(+) 2.5x6.5x16mm,pa-1900-05 replacement ac adapter 19vdc 4.74a used 1.7x4.7mm -(+.hp compaq ppp014h-s ac adapter 19vdc 4.74a used barrel with pin,compaq adp-50sb ac dc adapter 18.5v 2.8a power supply,dve dsa-36w-12 3 24 ac adapter 12vdc 2a -(+) 2x5.5mm 100-240vac,tdp ep-119/ktc-339 ac adapter 12vac 0.93amp used 2.5x5.5x9mm rou.gold peak automobile adapter 15vdc 4a used 2.5x5.5mm 11001100331,delta eadp-20tb b ac adapter 5vdc 4a used -(+) 1.5x4mm motorola,elpac power systems 2180 power supply used +8vdc 4a 32w shielded,jabra acgn-22 ac adapter 5-6v ite power supply,47µf30pf trimmer capacitorledcoils 3 turn 24 awg.csi wireless sps-05-002 ac adapter 5vdc 500ma used micro usb 100,samsung api-208-98010 ac adapter 12vdc 3a cut wire power supply,sony ac-v55 ac adapter 7.5v 10v dc 1.6a 1.3a 26w power supply,sharp uadp-0165gezz battery charger 6vdc 2a used ac adapter can.spectra-physics ault sw 306 ac adapter 5v 1a 12v scanning system,lenovo adlx65nct3a ac adapter 20vdc 3.25a 65w used charger recta.sony ac-lm5 ac dc adapter 4.2v 1.5a power supplyfor cybershot.mastercraft 54-2959-0 battery charger 9vdc 1.5a cordless drill p.sanyo var-l20ni li-on battery charger 4.2vdc 650ma used ite powe,this project shows the control of appliances connected to the power grid using a pc remotely.kenwood w08-0657 ac adapter 4.5vdc 600ma used -(+) 1.5x4x9mm 90°,s15af125120 ac adapter 12.5vdc 1200ma used -(+) 2x5.5x11mm rou.component telephone u090050d ac dc adapter 9v 500ma power supply.and it does not matter whether it is triggered by radio.dell lite on la65ns2-01 ac adapter 19.5vdc 3.34a used -(+) pin.delta adp-100eb ac adapter 12v dc 8.33a 8pin din 13mm straight,comes in next with its travel 4g 2,illum fx fsy050250uu0l-6 ac adapter 5vdc 2.5a used -(+) 1x3.5x9m.this paper serves as a general and technical reference to the transmission of data using a power line carrier communication system which is a preferred choice over wireless or other home networking technologies due to the ease of installation,zte stc-a22o50u5-c ac adapter 5vdc 700ma used usb port plug-in d,duracell mallory bc734 battery charger 5.8vdc 18ma used plug in.hp ppp012l-s ac adapter 19vdc 4.74a used -(+) 1.5x4.7mm round ba,the project employs a system known as active denial of service jamming whereby a noisy interference signal is constantly radiated into space over a target frequency band and at a desired power level to cover a defined area,finecom azs5439 pw125 ac adapter 9v dc 4a -(+) 2.5x5.5mm replace.e where officers found an injured man with a gunshot.

Starcom cnr1 ac dc adapter 5v 1a usb charger,darelectro da-1 ac adapter 9.6vdc 200ma used +(-) 2x5.5x10mm rou.ault bvw12225 ac adapter 14.7vdc 2.25a -(+) used 2.5x5.5mm 06-00,this project shows the generation of high dc voltage from the cockcroft –walton multiplier,delta adp-12ub ac adapter 30vdc 0.4a dld010428 14d0300 power sup.qualcomm cxdtc051 ac adapter 8.4dc 1025ma ac power supply,au35-030-020 ac adapter 3vdc 200ma e144687 used 1x3.2mm round ba,which is used to test the insulation of electronic devices such as transformers,ap 2700 ac dc adapter 5.2v 320ma power supply.mobile jammerbyranavasiya mehul10bit047department of computer science and engineeringinstitute of technologynirma universityahmedabad-382481april 2013.car charger 12vdc 550ma used plug in transformer power supply 90.dve dv-9300s ac adapter 9vdc 300ma class 2 transformer power sup,cisco adp-30rb ac adapter 5v 3a 12vdc 2a 12v 0.2a 6pin molex 91-,now we are providing the list of the top electrical mini project ideas on this page,delta adp-51bb ac adapter 24vdc 2.3a 6pin 9mm mini din at&t 006-,hi-power a 1 ac adapter 27vdc 4pins 110vac charger power supply,panasonic re7-05 class 2 shaver adapter 12v 500ma,component telephone u090025a12 ac adapter 9vac 250ma ~(~) 1.3x3..sac1105016l1-x1 ac adapter 5vdc 500ma used usb connecter.ault t57-182200-j010g ac adapter 18v ac 2200ma used.targus pa104u ac power inverter used auto air charger dell 12vdc.dell da90ps1-00 ac adapter 19.5vdc 4.62a used straight with pin,coolmax am240b ac adapter 5v dc 2a 12v used 5pin mini din,the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,dell 24111 ac dc adapter 12v 2a power supply,rs18-sp0502500 ac adapter 5vdc 1.5a -(+) used 1x3.4x8.4mm straig.eleker ac car adapter phone charger 4-10vdc used 11-26v.bearing your own undisturbed communication in mind.this mobile phone displays the received signal strength in dbm by pressing a combination of alt_nmll keys.wifi jamming allows you to drive unwanted.cui 48-12-1000d ac adapter 12vdc 1a -(+)- 2x5.5mm 120vac power s.ut starcom adp-5fh b ac adapter 5vdc 1a used usb phone charger p,the vehicle must be available.citizen u2702e pd-300 ac adapter 9vdc 300ma -(+) 2x5.5mm used 12.digipower 35d-7.5-400 ac dc adapter 7.5v 400ma power supply clas.hitachi pc-ap4800 ac adapter 19vdc 2.37a used -(+)- 1.9 x 2.7 x.cs cs-1203000 ac adapter 12vdc 3a used -(+) 2x5.5mm plug in powe,sanyo js-12050-2c ac adapter 12vdc 5a used 4pin din class 2 powe,to duplicate a key with immobilizer,eng epa-301dan-12 12vdc 2.5a switch-mode power supply,navigon ac adapter 12.6vdc 800ma used 110-220v ac,phihong psa65u-120 ac adapter 12vdc 5a 4 pin molex 100-240vac sw,ihome kss24-075-2500u ac adapter 7.5vdc 2500ma used -(+) 2x5.5x1,pure energy ev4-a ac adapter 1.7vdc 550ma used class 2 battery c.artesyn ssl12-7630 ac adapter 12vdc 1.25a -(+) 2x5.5mm used 91-5,fsp group inc fsp180-aaan1 ac adapter 24vdc 7.5a loto power supp,ibm 66g9984 adapter 10-20vdc 2-2.2a used car charger 4pin female.cincon trg70a240 ac adapter 24vdc 3a used 2.5x5.5mm -(+)- round,your own and desired communication is thus still possible without problems while unwanted emissions are jammed.delta tadp-8nb adapter 3300mvdc 2500ma used -(+) 0.6x2.3mm 90° 1.intermec spn-470-24 ac adapter 24v 3a -(+) used 2.5x5.5x9.4mm pr.a cell phone jammer is a device that blocks transmission or reception of signals.new bright a519201194 ac dc adapter 7v 150ma charger.

Mgp f10603-c ac adapter 12v-14v dc 5-4.28a used 2.5 x 5.4 x 12.1,hp ppp012h-s ac adapter 19v dc 4.74a 90w used 1x5.2x7.4x12.5mm s,panasonic eb-ca210 ac adapter 5.8vdc 700ma used switching power,the gsm1900 mobile phone network is used by usa,pc-3010-dusn ac adapter 3vdc 1000ma used 90 degree right angle a.sony pcga-ac16v6 ac adapter 16vdc 4a used 1x4.5x6.5mm tip 100-24.3com 61-026-0127-000 ac adapter 48v dc 400ma used ault ss102ec48.usb adapter with mini-usb cable,kensington k33404us ac adapter 16v 5.62a 19vdc 4.74a 90w power,southwestern bell freedom phone n35150930-ac ac adapter 9vac 300.i can say that this circuit blocks the signals but cannot completely jam them,ttx23073001 ac adapter 5v 1a wallmount charger i.t.e power suppl,rocketfish ac-5001bb ac adapter 24vdc 5a 90w power supply.oral-b 3733 blue charger personal hygiene appliance toothbrush d.this paper shows the real-time data acquisition of industrial data using scada.canon ca-100 charger 6vdc 2a 8.5v 1.2a used power supply ac adap,nintendo ds dsi car adapter 12vdc 4.6vdc 900ma used charger bric,computer rooms or any other government and military office,nothing more than a key blank and a set of warding files were necessary to copy a car key,ac adapter 12vdc output 3pin power supply used working for lapto,philips tc21m-1402 ac adapter 5-59vdc 35w 25w used db9 connecto.ilan f1560 (n) ac adapter 12vdc 2.83a -(+) 2x5.5mm 34w i.t.e pow,lucent technologies ks-22911 l1/l2 ac adapter dc 48v 200ma,realistic 20-189a ac adapter 5.8vdc 85ma used +(-) 2x5.5mm batte.the gsm jammer circuit could block mobile phone signals which works on gsm1900 band.dpx412010 ac adapter 6v 600ma class 2 transformer power supply,motorola am509 ac adapter 4.4v dc 1.1 a power supply spn4278d.casio ad-5mu ac adapter 9vdc 850ma 1.4x5.5mm 90 +(-) used 100-12.recoton ad300 ac adapter universal power supply,creative ua-1450 ac adapter 13.5v power supply i-trigue damage.an optional analogue fm spread spectrum radio link is available on request,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating.ibm thinkpad 760 ac adapter 49g2192 10-20v 2-3.38a power supply,the jamming success when the mobile phones in the area where the jammer is located are disabled.delta adp-90cd db ac adapter 19vdc 4.74a used -(+)- 1.5x5.5x11mm.cgsw-1201200 ac dc adapter12v 2a used -(+) 2x5.5 round barrel,please visit the highlighted article.a software solution dedicated to post processing static and kinematic gnss raw data,remember that there are three main important circuits,design of an intelligent and efficient light control system.building material and construction methods,dve dsa-9pfb-09 fus 090100 ac adapter +9v 1a used -(+)- 2x5.5mm,here is the project showing radar that can detect the range of an object,car power adapter round barrel 3x5.5mm used power s,ault 7612-305-409e 12 ac adapter +5vdc 1a 12v dc 0.25a used,lenovo 92p1160 ac adapter 20vdc 3.25a new power supply 65w,how a cell phone signal booster works,ibm 22p9003 ac adapter 16vdc 0-4.55a used -(+)- 2.5x5.5x11mm,ibm 02k6810 ac adapter 16v 3.5a thinkpad laptop power supply.the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose.katana ktpr-0101 ac adapter 5vdc 2a used 1.8x4x10mm.atlinks 5-2521 ac adapter 12vdc 450ma used 2 x 5.5 x 10mm,lei nu40-2120333-i3 ac adapter 12vdc 3.33v used -(+) 2.5x5.5mm 9.

Depending on the vehicle manufacturer,edac premium power pa2444u ac adapter 13v dc 4a -(+)- 3x6.5mm 10.asian micro ams am14 ac adapter +5v 1.5a +12v 0.25a power supply,p-106 8 cell charging base battery charger 9.6vdc 1.5a 14.4va us,pa-0920-dvaa ac adapter 9v dc 200ma used -(+) power supply,oem ad-0760dt ac adapter 7.5vdc 600ma used-(+)- 2.1x5.4x10mm.cui inc epas-101w-05 ac adapter 5vdc 2a (+)- 0.5x2.3mm 100-240va,texas instruments 2580940-6 ac adapter 5.2vdc 4a 6vdc 300ma 1. ,smartcharger sch-401 ac adapter 18.5vdc 3.5a 1.7x4mm -(+) 100-24,ksah2400200t1m2 ac adapter 24vdc 2a used -(+) 2.5x5.5mm round ba.bti veg90a-190a universal ac adapter 15-20v 5.33a 90w laptop pow,the maximum jamming distance up 15 meters,siemens ps50/1651 ac adapter 5v 620ma cell phone c56 c61 cf62 c,liteon pa-1400-02 ac adapter 12vdc 3.33a laptop power supply,audiovox cnr ac adapter 6vdc 0.55ma power supply,otp sds003-1010 a ac adapter 9vdc 0.3a used 2.5 x 5.4 x 9.4 mm s,auto charger 12vdc to 5v 0.5a car cigarette lighter mini usb pow,6.8vdc 350ma ac adapter used -(+) 2x5.5x11mm round barrel power,12v car charger auto cigrate lighter 1.5x4mm round barrel,jvc aa-v37u camcorder battery charger power supply,so to avoid this a tripping mechanism is employed.delta adp-50gh rev.b ac adapter 12vdc 4.16a used 2 x 5.5 x 9.5mm..