2021/08/06
By Kyle Wesson, Daniel Shepard, and Todd Humphreys
Disruption created by intentional generation of fake GPS signals could have serious economic consequences. This article discusses how typical civil GPS receivers respond to an advanced civil GPS spoofing attack, and four techniques to counter such attacks: spread-spectrum security codes, navigation message authentication, dual-receiver correlation of military signals, and vestigial signal defense. Unfortunately, any kind of anti-spoofing, however necessary, is a tough sell.
GPS spoofing has become a hot topic. At the 2011 Institute of Navigation (ION) GNSS conference, 18 papers discussed spoofing, compared with the same number over the past decade. ION-GNSS also featured its first panel session on anti-spoofing, called “Improving Security of GNSS Receivers,” which offered six security experts a forum to debate the most promising anti-spoofing technologies.
The spoofing threat has also drawn renewed U.S. government scrutiny since the initial findings of the 2001 Volpe Report. In November 2010, the U.S. Position Navigation and Timing National Executive Committee requested that the U.S. Department of Homeland Security (DHS) conduct a comprehensive risk assessment on the use of civil GPS. In February 2011, the DHS Homeland Infrastructure Threat and Risk Analysis Center began its investigation in conjunction with subject-matter experts in academia, finance, power, and telecommunications, among others. Their findings will be summarized in two forthcoming reports, one on the spoofing and jamming threat and the other on possible mitigation techniques. The reports are anticipated to show that GPS disruption due to spoofing or jamming could have serious economic consequences.
Effective techniques exist to defend receivers against spoofing attacks. This article summarizes state-of-the-art anti-spoofing techniques and suggests a path forward to equip civil GPS receivers with these defenses. We start with an analysis of a typical civil GPS receiver’s response to our laboratory’s powerful spoofing device. This will illustrate the range of freedom a spoofer has when commandeering a victim receiver’s tracking loops. We will then provide an overview of promising cryptographic and non-cryptographic anti-spoofing techniques and highlight the obstacles that impede their widespread adoption.
The Spoofing Threat
Spoofing is the transmission of matched-GPS-signal-structure interference in an attempt to commandeer the tracking loops of a victim receiver and thereby manipulate the receiver’s timing or navigation solution. A spoofer can transmit its counterfeit signals from a stand-off distance of several hundred meters or it can be co-located with its victim.
Spoofing attacks can be classified as simple, intermediate, or sophisticated in terms of their effectiveness and subtlety. In 2003, the Vulnerability Assessment Team at Argonne National Laboratory carried off a successful simple attack in which they programmed a GPS signal simulator to broadcast high-powered counterfeit GPS signals toward a victim receiver. Although such a simple attack is easy to mount, the equipment is expensive, and the attack is readily detected because the counterfeit signals are not synchronized to their authentic counterparts.
In an intermediate spoofing attack, a spoofer synchronizes its counterfeit signals with the authentic GPS signals so they are code-phase-aligned at the target receiver. This method requires a spoofer to determine the position and velocity of the victim receiver, but it affords the spoofer a serious advantage: the attack is difficult to detect and mitigate.
The sophisticated attack involves a network of coordinated intermediate-type spoofers that replicate not only the content and mutual alignment of visible GPS signals but also their spatial distribution, thus fooling even multi-antenna spoofing defenses.
Table 1. Comparison of anti-spoofing techniques discussed in this article.
Lab Attack. So far, no open literature has reported development or research into the sophisticated attack. This is likely because of the success of the intermediate-type attack: to date, no civil GPS receiver tested in our laboratory has fended off an intermediate-type spoofing attack. The spoofing attacks, which are always conducted via coaxial cable or in radio-frequency test enclosures, are performed with our laboratory’s receiver-spoofer, an advanced version of the one introduced at the 2008 ION-GNSS conference (see “Assessing the Spoofing Threat,” GPS World, January 2009).
To commence the attack, the spoofer transmits its counterfeit signals in code-phase alignment with the authentic signals but at power level below the noise floor. The spoofer then increases the power of the spoofed signals so that they are slightly greater than the power of the authentic signals. At this point, the spoofer has taken control of the victim receiver’s tracking loops and can slowly lead the spoofed signals away from the authentic signals, carrying the receiver’s tracking loops with it. Once the spoofed signals have moved more than 600 meters in position or 2 microseconds in time away from the authentic signals, the receiver can be considered completely owned by the spoofer.
Spoofing testbed at the University of Texas Radionavigation Laboratory, an advanced and powerful suite for anti-spoofing research. On the right are several of the civil GPS receivers tested and the radio-frequency test enclosure, and on the left are the phasor measurement unit and the civil GPS spoofer.
Although our spoofer fooled all of the receivers tested in our laboratory, there are significant differences between receivers’ dynamic responses to spoofing attacks. It is important to understand the types of dynamics that a spoofer can induce in a target receiver to gain insight into the actual dangers that a spoofing attack poses rather than rely on unrealistic assumptions or models of a spoofing attack. For example, a recent paper on time-stamp manipulation of the U.S. power grid assumed that there was no limit to the rate of change that a spoofer could impose on a victim receiver’s position and timing solution, which led to unrealistic conclusions.
Experiments performed in our laboratory sought to answer three specific questions regarding spoofer-induced dynamics:
How quickly can a timing or position bias be introduced?
What kinds of oscillations can a spoofer cause in a receiver’s position and timing?
How different are receiver responses to spoofing?
These questions were answered by determining the maximum spoofer-induced pseudorange acceleration that can be used to reach a certain final velocity when starting from a velocity of zero, without raising any alarms or causing the target receiver to lose satellite lock. The curve in the velocity-acceleration plane created by connecting these points defines the upper bound of a region within which the spoofer can safely manipulate the target receiver. These data points can be obtained empirically and fit to an exponential curve. Alarms on the receiver may cause some deviations from this curve depending on the particular receiver.
Figure 1 shows an example of the velocity-acceleration curve for a high-quality handheld receiver, whose position and timing solution can be manipulated quite aggressively during a spoofing attack. These results suggest that the receiver’s robustness — its ability to provide navigation and timing solutions despite extreme signal dynamics — is actually a liability in regard to spoofing. The receiver’s ability to track high accelerations and velocities allows a spoofer to aggressively manipulate its navigation solution.
Figure 1. Theoretical and experimental test results for a high-quality handheld receiver’s dynamic response to a spoofing attack. Although not shown here, the maximum attainable velocity is around 1,300 meters/second.
The relative ease with which a spoofer can manipulate some GPS receivers suggests that GPS-dependent infrastructure is vulnerable. For example, the telecommunications network and the power grid both rely on GPS time-reference receivers for accurate timing. Our laboratory has performed tests on such receivers to determine the disruptions that a successful spoofing attack could cause. The remainder of this section highlights threats to these two sectors of critical national infrastructure.
Cell-Phone Vulnerability. Code division multiple access (CDMA) cell-phone towers rely on GPS timing for tower-to-tower synchronization. Synchronization prevents towers from interfering with one another and enables call hand-off between towers. If a particular tower’s time estimate deviates more than 10 microseconds from GPS time, hand-off to and from that tower is disrupted. Our tests indicate that a spoofer could induce a 10-microsecond time deviation within about 30 minutes for a typical CDMA tower setup. A spoofer, or spoofer network, could also cause multiple neighboring towers to interfere with one another. This is possible because CDMA cell-phone towers all use the same spreading code and distinguish themselves only by the phasing (that is, time offset) of their spreading codes. Furthermore, it appears that a spoofer could impair CDMA-based E911 user-location.
Power-Grid Vulnerability. Like the cellular network, the power grid of the future will rely on accurate GPS time-stamps. The efficiency of power distribution across the grid can be improved with real-time measurements of the voltage and current phasors. Phasor measurement units (PMUs) have been proposed as a smart-grid technology for precisely this purpose. PMUs rely on GPS to time-stamp their measurements, which are sent back to a central monitoring station for processing. Currently, PMUs are used for closed-loop grid control in only a few applications, but power-grid modernization efforts will likely rely more heavily on PMUs for control. If a spoofer manipulates a PMU’s time stamps, it could cause spurious variations in measured phase angles. These variations could distort power flow or stability estimates in such a way that grid operators would take incorrect or unnecessary control actions including powering up or shutting down generators, potentially causing blackouts or damage to power-grid equipment.
Under normal circumstances, a changing separation in the phase angle between two PMUs indicates changes in power flow between the regions measured by each PMU. Tests demonstrate that a spoofer could cause variations in a PMU’s measured voltage phase angle at a rate of 1.73 degrees per minute. Thus, a spoofing attack could create the false indications of power flow across the grid. The tests results also reveal, however, that it is impossible for a spoofer to cause changes in small-signal grid stability estimates, which would require the spoofer to induce rapid (for example, 0.1–3 Hz) microsecond-amplitude oscillations in timing. Such oscillations correspond to spoofing dynamics well outside the region of freedom of all receivers we have tested. A spoofer might also be able to affect fault-location estimates obtained through time-difference-of-arrival techniques using PMU measurements. This could cause large errors in fault-location estimates and hamper repair efforts.
What Can Be Done? Despite the success of the intermediate-type spoofing attack against a wide variety of civil GPS receivers and the known vulnerabilities of GPS-dependent critical infrastructure to spoofing attacks, anti-spoofing techniques exist that would enable receivers to successfully defend themselves against such attacks. We now turn to four promising anti-spoofing techniques.
Cryptographic Methods
These techniques enable a receiver to differentiate authentic GPS signals from counterfeit signals with high likelihood. Cryptographic strategies rely on the unpredictability of so-called security codes that modulate the GPS signal. An unpredictable code forces a spoofer who wishes to mount a successful spoofing attack to either
estimate the unpredictable chips on-the-fly, or
record and play back authentic GPS spectrum (a meaconing attack).
To avoid unrealistic expectations, it should be noted that no anti-spoofing technique is completely impervious to spoofing. GPS signal authentication is inherently probabilistic, even when rooted in cryptography. Many separate detectors and cross-checks, each with its own probability of false alarm, are involved in cryptographic spoofing detection. Figure 2 illustrates how the jammer-to-noise ratio detector, timing consistency check, security-code estimation and replay attack (SCER) detector, and cryptographic verification block all work together. This hybrid combination of statistical hypothesis tests and Boolean logic demonstrates the complexities and subtleties behind a comprehensive, probabilistic GPS signal authentication strategy for security-enhanced signals.
Figure 2. GNSS receiver components required for GNSS signal authentication. Components that support code origin authentication are outlined in bold and have a gray fill, whereas components that support code timing authentication are outlined in bold and have no fill. The schematic assumes a security code based on navigation message authentication.
Spread Spectrum Security Codes. In 2003, Logan Scott proposed a cryptographic anti-spoofing technique based on spread spectrum security codes (SSSCs). The most recent proposed version of this technique targets the L1C signal, which will be broadcast on GPS Block III satellites, because the L1C waveform is not yet finalized. Unpredictable SSSCs could be interleaved with the L1C spreading code on the L1C data channel, as illustrated in Figure 3. Since L1C acquisition and tracking occurs on the pilot channel, the presence of the SSSCs has negligible impact on receivers. Once tracking L1C, a receiver can predict when the next SSSC will be broadcast but not its exact sequence. Upon reception of an SSSC, the receiver stores the front-end samples corresponding to the SSSC interval in memory. Sometime later, the cryptographic digital key that generated the SSSC is transmitted over the navigation message. With knowledge of the digital key, the receiver generates a copy of the actual transmitted SSSC and correlates it with the previously-recorded digital samples. Spoofing is declared if the correlation power falls below a pre-determined threshold.
Figure 3. Placement of the periodically unpredictable spread spectrum security codes in the GPS L1C data channel spreading sequence.
When the security-code chip interval is short (high chipping rate), it is difficult for a spoofer to estimate and replay the security code in real time. Thus, the SSSC technique on L1C offers a strong spoofing defense since the L1C chipping rate is high (that is, 1.023 MChips/second). Furthermore, the SSSC technique does not rely on the receiver obtaining additional information from a side channel; all the relevant codes and keys are broadcast over the secured GPS signals. Of course a disadvantage for SSSC is that it requires a fairly fundamental change to the currently-proposed L1C definition: the L1C spreading codes must be altered.
Implementation of the SSSC technique faces long odds, partly because it is late in the L1C planning schedule to introduce a change to the spreading codes. Nonetheless, in September 2011, Logan Scott and Phillip Ward advocated for SSSC at the Public Interface Control Working Group meeting, passing the first of many wickets. The proposal and associated Request for Change document will now proceed to the Lower Level GPS Engineering Requirements Branch for further technical review. If approved there, it passes to the Joint Change Review Board for additional review and, if again approved, to the Technical Interchange Meeting for further consideration. The chances that the SSSC proposal will survive this gauntlet would be much improved if some government agency made a formal request to the GPS Directorate to include SSSCs in L1C — and provided the funding to do so. The DHS seems to us a logical sponsoring agency.
Navigation Message Authentication. If an L1C SSSC implementation proves unworkable, an alternative, less-invasive cryptographic authentication scheme based on navigation message authentication (NMA) represents a strong fall-back option. In the same 2003 ION-GNSS paper that he proposed SSSC, Logan Scott also proposed NMA. His paper was preceded by an internal study at MITRE and followed by other publications in the open literature, all of which found merit in the NMA approach. The NMA technique embeds public-key digital signatures into the flexible GPS civil navigation (CNAV) message, which offers a convenient conveyance for such signatures. The CNAV format was designed to be extensible so that new messages can be defined within the framework of the GPS Interference Specification (IS). The current GPS IS defines only 15 of 64 CNAV messages, reserving the undefined 49 CNAV messages for future use.
Our lab recently demonstrated that NMA works to authenticate not only the navigation message but also the underlying signal. In other words, NMA can be the basis of comprehensive signal authentication. We have proposed a specific implementation of NMA that is packaged for immediate adoption. Our proposal defines two new CNAV messages that deliver a standardized public-key elliptic-curve digital algorithm (ECDSA) signature via the message format in Figure 4.
Figure 4. Format of the proposed CNAV ECDSA signature message, which delivers the first or second half of the 466-bit ECDSA signature and a 5-bit salt in the 238-bit payload field.
Although the CNAV message format is flexible, it is not without constraints. The shortest block of data in which a complete signature can be embedded is a 96-second signature block such as the one shown in Figure 5. In this structure, the two CNAV signature messages are interleaved between the ephemeris and clock data to meet the broadcast requirements.
Figure 5. The shortest broadcast signature block that does not violate the CNAV ephemeris and timing broadcast requirements. To meet the required broadcast interval of 48 seconds for message types 10, 11, and one of 30–39, the ECDSA signature is broadcast over a 96-second signature block that is composed of eight CNAV messages.
The choice of the duration between signature blocks is a tradeoff between offering frequent authentication and maintaining a low percentage of the CNAV message reserved for the digital signature. In our proposal, signature blocks are transmitted roughly every five minutes (Figure 6) so that only 7.5 percent of the navigation message is devoted to the digital signature. Across the GPS constellation, the signature block could be offset so that a receiver could authenticate at least one channel approximately every 30 seconds. Like SSSC, our proposed version of NMA does not require a receiver’s getting additional information from a side channel, provided the receiver obtains public key updates on a yearly basis.
Figure 6. A signed 336-second broadcast. The proposed strategy signs every 28 CNAV messages with a signature broadcast over two CNAV messages on each broadcast channel.
NMA is inherently less secure than SSSC. A NMA security code chip interval (that is, 20 milliseconds) is longer than a SSSC chip interval, thereby allowing the spoofer more time to estimate the digital signature on-the-fly. That is not to say, however, that NMA is ineffective. In fact, tests with our laboratory’s spoofing testbed demonstrated the NMA-based signal authentication structure described earlier offered a receiver a better-than 95 percent probability of detecting a spoofing attack for a 0.01 percent probability of false alarm under a challenging spoofing-attack scenario.
NMA is best viewed as a hedge. If the SSSC approach does not gain traction, then NMA might, since it only requires defining two new CNAV messages in the GPS IS — a relatively minor modification. CNAV-based NMA could defend receivers tracking L2C and L5. A new CNAV2 message will eventually be broadcast on L1 via L1C, so a repackaged CNAV2-based NMA technique could offer even single-frequency L1 receivers a signal-side anti-spoofing defense.
P(Y) Code Dual-Receiver Correlation. This approach avoids entirely the issue of GPS IS modifications. The technique correlates the unknown encrypted military P(Y) code between two civil GPS receivers, exploiting known carrier-phase and code-phase relationships. It is similar to the dual-frequency codeless and semi-codeless techniques that civil GPS receivers apply to track the P(Y) code on L2. Peter Levin and others filed a patent on the codeless-based signal authentication technique in 2008; Mark Psiaki extended the approach to semicodeless correlation and narrow-band receivers in a 2011 ION-GNSS paper.
In the dual-receiver technique, one receiver, stationed in a secure location, tracks the authentic L1 C/A codes while receiving the encrypted P(Y) code. The secure receiver exploits the known timing and phase relationships between the C/A code and P(Y) code to isolate the P(Y) code, of which it sends raw samples (codeless technique) or estimates of the encrypting W-code chips (semi-codeless technique) over a secure network to the defending receiver. The defending receiver correlates its locally-extracted P(Y) with the samples or W-code estimates from the secure receiver. If a spoofing attack is underway, the correlation power will drop below a statistical threshold, thereby causing the defending receiver to declare a spoofing attack. Although the P(Y) code is 20 MHz wide, a narrowband civil GPS receiver with 2.6 MHz bandwidth can still perform the statistical hypothesis tests even with the resulting 5.5 dB attenuation of the P(Y) code. Because the dual-receiver method can run continuously in the background as part of a receiver’s standard GPS signal processing, it can declare a spoofing attack within seconds — a valuable feature for many applications.
Two considerations about the dual-receiver technique are worth noting. First, the secure receiver must be protected from spoofing for the technique to succeed. Second, the technique requires a secure communication link between the two receivers. Although the first requirement is easily achieved by locating secure receivers in secure locations, the second requirement makes the technique impractical for some applications that cannot support a continuous communication link.
Of all the proposed cryptographic anti-spoofing techniques, only the dual-receiver method could be implemented today. Unfortunately the P(Y) code will no longer exist after 2021, meaning that systems that make use of the P(Y)-based dual-receiver technique will be rendered unprotected, although a similar M-code-based technique could be an effective replacement. The dual-receiver method, therefore, is best thought of as a stop-gap: it can provide civil GPS receivers with an effective anti-spoofing technique today until a signal-side civil GPS authentication technique is approved and implemented in the future This sentiment was the consensus of the panel experts at the 2011 ION-GNSS session on civil GPS receiver security.
Non-Cryptographic Methods
Non-cryptographic techniques are enticing because they can be made receiver-autonomous, requiring neither security-enhanced civil GPS signals nor a side-channel communication link. The literature contains a number of proposed non-cryptographic anti-spoofing techniques. Frequently, however, these techniques rely on additional hardware, such as accelerometers or inertial measurements units, which may exceed the cost, size, or weight requirements in many applications. This motivates research to develop software-based, receiver-autonomous anti-spoofing methods.
Vestigial Signal Defense (VSD). This software-based, receiver-autonomous anti-spoofing technique relies on the difficulty of suppressing the true GPS signal during a spoofing attack. Unless the spoofer generates a phase-aligned nulling signal at the phase center of the victim GPS receiver’s antenna, a vestige of the authentic signal remains and manifests as a distortion of the complex correlation function. VSD monitors distortion in the complex correlation domain to determine if a spoofing attack is underway.
To be an effective defense, the VSD must overcome a significant challenge: it must distinguish between spoofing and multipath. The interaction of the authentic and spoofed GPS signals is similar to the interaction of direct-path and multipath GPS signals. Our most recent work on the VSD suggests that differentiating spoofing from multipath is enough of a challenge that the goal of the VSD should only be to reduce the degrees-of-freedom available to a spoofer, forcing the spoofer to act in a way that makes the spoofing signal or vestige of the authentic GPS signal mimic multipath. In other words, the VSD seeks to corner the spoofer and reduce its space of possible dynamics.
Among other options, two potential effective VSD techniques are
a maximum-likelihood bistatic-radar-based approach and
a phase-pseudorange consistency check.
The first approach examines the spatial and temporal consistency of the received signals to detect inconsistencies between the instantaneous received multipath and the typical multipath background environment. The second approach, which is similar to receiver autonomous integrity monitoring (RAIM) techniques, monitors phase and pseudorange observables to detect inconsistencies potentially caused by spoofing. Again, a spoofer can act like multipath to avoid detection, but this means that the VSD would have achieved its modest goal.
Anti-Spoofing Reality Check
Security is a tough sell. Although promising anti-spoofing techniques exist, the reality is that no anti-spoofing techniques currently defend civil GPS receivers. All anti-spoofing techniques face hurdles. A primary challenge for any technique that proposes modifying current or proposed GPS signals is the tremendous inertia behind GPS signal definitions. Given the several review boards whose approval an SSSC or NMA approach would have to gain, the most feasible near-term cryptographic anti-spoofing technique is the dual-receiver method. A receiver-autonomous, non-cryptographic approach, such as the VSD, also warrants further development. But ultimately, the SSSC or NMA techniques should be implemented: a signal-side civil GPS cryptographic anti-spoofing technique would be of great benefit in protecting civil GPS receivers from spoofing attacks.
Manufacturers
The high-quality handheld receiver cited in Figure 1 was a Trimble Juno SB. Testbed equipment shown: Schweitzer Engineering Laboratories SEL-421 synchrophasor measurement unit; Ramsey STE 3000 radio-frequency test chamber; Ettus Research USRP N200 universal software radio peripheral; Schweitzer SEL-2401 satellite-synchronized clock (blue); Trimble Resolution SMT receiver (silver); HP GPS time and frequency reference receiver.
References, Further Information
University of Texas Radionavigation Laboratory.
Full results of Figure 1 experiment are given in Shepard, D.P. and T.E. Humphreys, “Characterization of Receiver Response to Spoofing Attacks,” Proceedings of ION-GNSS 2011.
NMA can be the basis of comprehensive signal authentication: Wesson, K.D., M. Rothlisberger, T. E. Humphreys (2011), “Practical cryptographic civil GPS signal authentication,” Navigation, Journal of the ION, submitted for review.
Humphreys, T.E, “Detection Strategy for Cryptographic GNSS Anti-Spoofing,” IEEE Transactions on Aerospace and Electronic Systems, 2011, submitted for review.
Kyle Wesson is pursuing his M.S. and Ph.D. degrees in electrical and computer engineering at the University of Texas at Austin. He is a member of the Radionavigation Laboratory. He received his B.S. from Cornell University.
Daniel Shepard is pursuing his M.S. and Ph.D. degrees in aerospace engineering at the University of Texas at Austin, where he also received his B.S. He is a member of the Radionavigation Laboratory.
Todd Humphreys is an assistant professor in the department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin and director of the Radionavigation Laboratory. He received a Ph.D. in aerospace engineering from Cornell University.
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Delta electronics adp-36db rev.a ac power adapter ast laptop,this project shows charging a battery wirelessly.infinite ad30-5 ac adapter 5vdc 6a 3pin power supply,ibm 92p1105 ac adapter 19vdc 4.74a 5.5x7.9mm -(+) used 100-240va,ac adapter 5.2vdc 450ma used usb connector switching power supp.directed dsa-36w-12 36 ac adapter +12vdc 3a 2.1mm power supply,toshiba pa-1750-09 ac adapter 19vdc 3.95a used -(+) 2.5x5.5x12mm,power grid control through pc scada,hp ppp014h ac adapter 18.5vdc 4.9a -(+) 1.8x4.75mm bullet used 3.it will be a wifi jammer only.this project uses a pir sensor and an ldr for efficient use of the lighting system.grundig nt473 ac adapter 3.1vdc 0.35a 4vdc 0.60a charging unit l,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way,offers refill reminders and pickup notifications.2 w output powerwifi 2400 – 2485 mhz.umec up0301a-05p ac adapter 5vdc 6a 30w desktop power supply,cisco aa25480l ac adapter 48vdc 380ma used 2.5x5.5mm 90° -(+) po,a mobile jammer is an instrument used to protect the cell phones from the receiving signal.ahead jad-1201000e ac adapter 12vdc 1000ma 220vac european vers,we are introducing our new product that is spy mobile phone jammer in painting,hi capacity ac-5001 ac adapter 15-24v dc 90w new 3x6.3x11mm atta,sam a460 ac adapter 5vdc 700ma used 1x2.5mm straight round barre,ge tl26511 0200 rechargeable battery 2.4vdc 1.5mah for sanyo pc-,liteon pa-1600-05 ac adapter 19v dc 3.16a 60w averatec adp68,law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,extra shipping charges for international buyers partial s&h paym,uniross ad101704 ac adapter 3, 4, 5, 5, 6, 9, 12v 0.8a 9.6va use,ault 7612-305-409e 12 ac adapter +5vdc 1a 12v dc 0.25a used,blackberry psm24m-120c ac adapter 12vdc 2a used rapid charger 10,phihong psc30u-120 ac adapter 12vdc 2.5a extern hdd lcd monitor.i introductioncell phones are everywhere these days.li shin lse9802a2060 ac adapter 20vdc 3a 60w max -(+)- used.scope dj04v20500a battery charger 4.2vdc 500ma used 100-240v ac.hp ppp016c ac adapter 18.5vdc 6.5a 120w used.2100 to 2200 mhzoutput power.citizen ad-420 ac adapter 9vdc 350ma used 2 x 5.5 x 9.6mm.kensington k33403 ac dc power adapter 90w with usb port notebook,usei am-9300 ac adapter 5vdc 1.5a ac adapter plug-in class 2 tra,sony psp-180 dc car adapter 5vdc 2000ma used -(+) 1.5x4mm 90° ro,foxlink fa-4f020 ac adapter 6vdc 1a used -(+) 1.5x4x8.4mm 90° ro,whose sole purpose is to inhibit the use of mobiles,dell aa20031 ac adapter 20vdc 3.5a 70w dell latitude c series,li shin international enterprise 0322b1224 ac adapter 12vdc 2a u,smartcharger sch-401 ac adapter 18.5vdc 3.5a 1.7x4mm -(+) 100-24.
Amigo ams4-1501600fu ac adapter 15vdc 1.6a -(+) 1.7x4.7mm 100-24,lexmark click cps020300050 ac adapter 30v 0.50a used class 2 tra,coming data cp0540 ac adapter 5vdc 4a -(+) 1.2x3.5mm 100-240vac,zw zw12v25a25rd ac adapter 12vdc 2.5a used -(+) 2.5x5.5mm round,creative ppi-0970-ul ac dc adapter 9v 700ma ite power supply.exact coverage control furthermore is enhanced through the unique feature of the jammer,accordingly the lights are switched on and off,biosystems 54-05-a0204 ac adapter 9vdc 1a used -(+) 2.5x5.5mm 12,aura i-143-bx002 ac adapter 2x11.5v 1.25a used 3 hole din pin,archer 273-1455 ac adapter used 9vdc 300ma -(+) 2x5.5x10mm.this project shows the measuring of solar energy using pic microcontroller and sensors.selectable on each band between 3 and 1,ppp003sd replacement ac adapter 18.5v 6.5a power supply oval pin,tyco rc c1897 ac adapter 8.5vdc 420ma 3.6w power supply for 7.2v,none reports/minutes 7 - 15 1,yh-u35060300a ac adapter 6vac 300ma used ~(~) 2x5.5mm straight r,this project shows the control of home appliances using dtmf technology.eleker ac car adapter phone charger 4-10vdc used 11-26v.apple adp-22-611-0394 ac adapter 18.5vdc 4.6a 5pin megnatic used.canon ch-3 ac adapter 5.8vdc 130ma used 2.5x5x10mm -(+)-.rio tesa5a-0501200d-b ac dc adapter 5v 1a usb charger.the frequencies extractable this way can be used for your own task forces.pa-1121-02hd replacement ac adapter 18.5v 6.5a laptop power supp,liteon pa-1750-07 ac adapter 15vdc 5a pa3283u-2aca pa3283e-2aca,lg sta-p53wr ac adapter 5.6v 0.4a direct plug in poweer supply c.foreen industries 28-a06-200 ac adapter 6vdc 200ma used 2x5.5mm,1 w output powertotal output power.psc 7-0564 pos 4 station battery charger powerscan rf datalogic,the output of each circuit section was tested with the oscilloscope.hp pa-1121-12r ac adapter 18.5vdc 6.5a used 2.5 x 5.5 x 12mm,wang wh-601e2ca-2 ac adapter 12vac 5a 60w used 2pin 120vac plug,this is the newly designed 22-antenna 5g jammer.ibm 02k6750 ac adapter 16vdc 4.5a used 2.5x5.5mm 100-240vac roun,cable shoppe inc oh-1048a0602500u-ul ac adapter 6vdc 2.5a used,here is the project showing radar that can detect the range of an object,p-056a rfu adapter power supply for use with playstation brick d,hp 384021-001 compaq ac adapter 19vdc 4.7a laptop power supply,three phase fault analysis with auto reset for temporary fault and trip for permanent fault,dell hp-af065b83 ow5420 ac adapter 19.5vdc 3.34a 65w laptop powe,the cell phone signal jamming device is the only one that is currently equipped with an lcd screen.ktec ksa0100500200d5 ac adapter 5vdc 2a used -(+) 1x3.4mm strai.ibm 02k7006 ac adapter 16vdc 3.36a used -(+)- 2.5x5.5mm 100-240v,changzhou un-d7.2v200 ac dc adapter 7.2vdc 200ma -(+) used 120va.citizen u2702e pd-300 ac adapter 9vdc 300ma -(+) 2x5.5mm used 12.
Olympus a511 ac adapter 5vdc 2a power supply for ir-300 camera,in the police apprehending those persons responsible for criminal activity in the community.2w power amplifier simply turns a tuning voltage in an extremely silent environment,3com 722-0004 ac adapter 3vdc 0.2a power supply palm pilot,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience.cui ka12d120045034u ac adapter 12vdc 450ma used -(+)- 2x5.5x10mm,texas instruments 2580940-6 ac adapter 5.2vdc 4a 6vdc 300ma 1,th 5vdc 11v used travel charger power supply 90-250vac phone.cad-10 car power adapter 12vdc used -(+) 1.5x4mm pdb-702 round b,mastercraft sa41-6a battery carger 7.2vdc used -(+) power supply.lind automobile apa-2691a 20vdc 2.5amps ibm thinkpad laptop powe,panasonic pqlv219 ac adapter 6.5vdc 500ma -(+) 1.7x4.7mm power s.delta adp-63bb b ac adapter 15v 4.2a laptop power supply,igo ps0087 dc auto airpower adapter 15-24vdc used no cable 70w,retrak whafr24084001 ac adapter 19vdc 3.42a used 4.2x6mm power s.5 kgadvanced modelhigher output powersmall sizecovers multiple frequency band,its called denial-of-service attack,simple mobile jammer circuit diagram.extra shipping charges for international buyers (postal service),aa41-120500 ac adapter 12vac 500ma used 1.9x5.5x12mm straight ro,2110 to 2170 mhztotal output power,is a robot operating system (ros),power amplifier and antenna connectors,oem aa-091a5bn ac adapter 9vac 1.5a used ~(~) 2x5.5mm europe pow.hp ppp018h ac adapter 19vdc 1.58a power suppply 534554-002 for c,motorola 481609oo3nt ac adapter 16vdc 900ma used 2.4x5.3x9.7mm,a software solution dedicated to post processing static and kinematic gnss raw data.pa-1650-02h replacement ac adapter 18.5v 3.5a for hp laptop powe.dell adp-150eb b ac adapter 19.5v dc 7700ma power supply for ins,asus ad59230 ac adapter 9.5vdc 2.315a laptop power supply,akii a05c1-05mp ac adapter +5vdc 1.6a used 3 x 5.5 x 9.4mm,delta adp-60db rev.b ac adapter 19vdc 3.16a used 3 x 5.5 x 9.6mm,motorola fmp5202c ac adapter 5v 850ma cell phone power supply.shanghai ps052100-dy ac adapter 5.2vdc 1a used (+) 2.5x5.5x10mm.delphi 41-6-1000d ac adapter 6vdc 1000ma skyfi skyfi2 xm radio.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.and frequency-hopping sequences,fujitsu ac adapter 19vdc 3.68 used 2.8 x 4 x 12.5mm,ku2b-120-0300d ac adapter 12vdc 300ma -o ■+ power supply c.motorola am509 ac adapter 4.4v dc 1.1 a power supply spn4278d,solex tri-pit 1640c ac adapter 16.5vac 40va 50w used screw termi.the rf cellular transmitted module with frequency in the range 800-2100mhz,hitachi pc-ap4800 ac adapter 19vdc 2.37a used -(+)- 1.9 x 2.7 x.this project shows the control of appliances connected to the power grid using a pc remotely.
2 w output power3g 2010 – 2170 mhz,motorola bc6lmvir01 class 2 radio battery charger used 11vdc 1.3,ch-91001-n ac adapter 9vdc 50ma used -(+) 2x5.5x9.5mm round barr.sunbeam gb-2 ac adapter 110-120vac used transformer shaver canad.aparalo electric 690-10931 ac adapter 9vdc 700ma 6.3w used -(+).altec lansing a1664 ac adapter 15vdc 800ma used -(+) 2x,deactivating the immobilizer or also programming an additional remote control,minolta ac-a10 vfk-970b1 ac adapter 9vdc 0.7a 2x5.5mm +(-) new 1,thomson 5-2603 ac adapter 9vdc 500ma used -(+) 2x5.5x12mm 90° ro,rca cps015 ac adapter9.6vdc 2.3a 12.5v 1.6a used camcorder bat,casio phone mate m/n-90 ac adapter 12vdc 200ma 6w white colour.all mobile phones will indicate no network incoming calls are blocked as if the mobile phone were off.lei power converter 220v 240vac 2000w used multi nation travel a,communication jamming devices were first developed and used by military.biogenik s12a02-050a200-06 ac adapter 5vdc 2a used -(+) 1.5x4x9m,000 dollar fine and one year in jail.you’ll need a lm1458 op amp and a lm386 low,compaq series 2862a ac adapter 16.5vdc 2.6a -(+) 2x5.5mm 100-240,this system also records the message if the user wants to leave any message,nec adp57 ac dc adapter 15v 4a 60w laptop versa lx lxi sx,ihomeu150150d51 ac adapter 15vdc 1500ma -(+) 2.1x5.5x10mm roun.compaq2882 213563-001 delta ac adapter 18vdclaptops lte 500.hp f1011a ac adapter 12vdc 0.75a used -(+)- 2.1x5.5 mm 90 degree.bothhand m1-8s05 ac adapter +5v 1.6a used 1.9 x 5.5 x 9.4mm,increase the generator's volume to play louder than,for any further cooperation you are kindly invited to let us know your demand.panasonic pv-a16-k video ac adapter 6v dc 2.2a 24w battery charg,preventively placed or rapidly mounted in the operational area,apd asian power adapter wa-30b19u ac adapter 19vdc 1.58a used 1..sanken seb55n2-16.0f ac adapter 16vdc 2.5a power supply,ad41-0900500du ac adapter 9vdc 500ma power supply,compaq pa-1530-02cv ac adapter 18.5vdc 2.7a used 1.7x5mm round b,wj-y482100400d ac adapter 21vdc 400ma used toolmaster battery ch,we now offer 2 mobile apps to help you.radio remote controls (remote detonation devices),sony battery charger bc-trm 8.4v dc 0.3a 2-409-913-01 digital ca,american telecom ku1b-090-0200d ac adapter 9vdc 200ma -(+)-used,circut ksah1800250t1m2 ac adapter 18vdc 2.5a 45w used -(+) 2.2x5.ad467912 multi-voltage car adapter 12vdc to 4.5, 6, 7.5, 9 v dc.cidco dv-9200 ac adapter 9vdc 200ma used -(+) 2.2x5.4mm straight,jhs-e02ab02-w08a ac adapter 5v 12vdc 2a used 6pin din power supp,samsung atadd030jbe ac adapter 4.75v 0.55a used,rocketfish kss12_120_1000u ac dc adapter 12v 1a i.t.e power supp,cge pa009ug01 ac adapter 9vdc 1a e313759 power supply.
V infinity emsa240167 ac adapter 24vdc 1.67a -(+) used 2x5.5mm s.skil ad35-06003 ac adapter 6v dc 300ma cga36 power supply cpq600.this project uses arduino for controlling the devices,lenovo 42t5276 ac adapter 20vdc 4.5a 90w used -(+)- 5.6x7.8mm st,5% to 90%modeling of the three-phase induction motor using simulink,grab high-effective mobile jammers online at the best prices on spy shop online.us robotics dv-9750-5 ac adapter 9.2vac 700ma used 2.5x 5.5mm ro.game elements gsps214 car adapter for playstaion 2condition: n,sector 5814207 ac adapter +5vdc 2a 5.4va used -(+) 1.5x2.5x9.8mm,fujitsu cp293662-01 ac adapter 19vdc 4.22a used 2.5 x 5.5 x 12mm.adjustable power phone jammer (18w) phone jammer next generation a desktop / portable / fixed device to help immobilize disturbance,touch m2-10us05-a ac adapter +5vdc 2a used -(+) 1x3.5x7mm round.jensen dv-1215-3508 ac adapter 12vdc 150ma used 90°stereo pin,cet technology 48a-18-1000 ac adapter 18vac 1000ma used transfor,delta eadp-12cb b ac adapter 12vdc 1a used 2.1 x 5.5 x 9mm.circuit-test ad-1280 ac adapter 12v dc 800ma new 9pin db9 female.ault pw118 ac adapter 5v 3a i.t.e power supply.depending on the vehicle manufacturer,lei mt12-y090100-a1 ac adapter 9vdc 1a used -(+) 2x5.5x9mm round,fsp fsp030-dqda1 ac adapter 19vdc 1.58a used -(+) 1.5x5.5x10mm r,plantronics ssa-5w-05 0us 050018f ac adapter 5vdc 180ma used usb,ibm aa19650 ac adapter 16vdc 2.2a class 2 power supply 85g6709,long range jammer free devices,lei mu12-2075150-a1 ac adapter 7.5v 1.5a power supply,mw48-1351000 ac adapter 13.5vdc 1a used 2 x 5.5 x 11mm,altas a-pa-1260315u ac adapter 15vdc 250ma -(+) 0.6x9.5 rf used,we hope this list of electrical mini project ideas is more helpful for many engineering students.including almost all mobile phone signals,xiamen keli sw-0209 ac adapter 24vdc 2000ma used -(+)- 2.5x5.5mm.spy mobile phone jammer in painting,sanyo scp-06adt ac adapter 5.4v dc 600ma used phone connector po.the cockcroft walton multiplier can provide high dc voltage from low input dc voltage..
