# Tag Info

## Hot answers tagged telecommunication

10

Your best option for wireless communication in this situation is some kind of optical link. Consumer microwaves typically operate at a frequency of 2.45 GHz and Bluetooth operates from 2.4 GHz to 2.485 GHz, so any shield you design for one will be equally effective for the other. You could design a Faraday cage which gives you enough suppression at 2.45 ...

10

Cross-interference between aircraft is a high unlikely event because all commercial aircraft designs have to pass DO-160 environmental testing requirements. Among the DO-160 testing specification is EMI/EMC Testing. These tests include Radiated Emission, Interference and Immunity Testing. Part of these tests are to answer "Two aircraft are very close ...

9

To add to what Russell said, it would take a very stupidly designed protocol to allow the comands from one aircraft to control the other, even assuming that cross-reception is good. As a everyday example, think of a bunch of people talking on cell phones standing near each other. One person accidentally receiving another's conversation just doesn't happen. ...

8

Modern communications systems are able to achieve essentially any desired data rate and degree of message integrity in any well-enough-defined environment. It's "just a matter" of the degree of effort, complexity and $that are needed. Designing a system to meet any desired data rate, number of users, and integrity is thus "just a matter of engineering". ... 7 With regard to protecting active electronics inside the oven, you have the choice of either absorbing the microwaves (e.g., water jacket) or reflecting the microwaves (any high-conductivity metal). Any sort of reflector for microwaves inside an oven must be designed very carefully, because there's a good chance of creating unwanted "hot spots" and/or areas ... 7 I will leave the main part of the previous answer below, as it contains more information about the differences between several radio protocols. As for the differences between Zigbee 3.0 and Z-Wave, let's do a side by side comparison: Frequency: Zigbee uses the 2.4GHz band, while Z-wave uses the 868MHz band in Europe and the 900MHz ISM band in the US (see ... 7 From: Engineers Garage Dual Tone Multi-Frequency:$f_1$= 697Hz, 770Hz, 852Hz, 941Hz.$f_2$= 1209Hz, 1336Hz, 1477Hz, 1633Hz. A key press on a DTMF keypad means a combination of$f_1$and$f_2$(Dual Tone) frequencies are heard at the same time.$f_1$(rows) and$f_2$(columns) have four frequencies (Multi-Frequency) associated with them, although 1633Hz ... 6 As you might have already realized there is a good reason that some of Bluetooth headset are inexpensive. Poor design. High quality, well designed Bluetooth headset tend to be expensive. Also not all expensive Bluetooth headsets are high quality. While it is difficult to root cause failures without physically analyzing the hardware, I will provide some ... 6 If you could truly indefinitely keep a line open for anyone who calls you, by simply not hanging up on your end, the potential for abuse is endless. That's the way the POTS (plain old telephone system) worked. The caller controlled the line. This "feature" was exploited by criminals who called the police stations from phone boxes and ripped the handsets ... 5 No, crossed communications would be a total non-issue. Think of it like a home wireless network. All your devices at home can talk to each other on your WiFi network, and the same is true for your neighbour. But your devices can't talk to your neighbour's devices because they are on a different wireless network. Such wireless networks in planes would have ... 4 There is information out there, but probably the best way to find out is to actually try it. Grab a small Bluetooth or Wifi device and seal it in a waterproof enclosure or bag, and submerge it to the bottom of the fish bowl under water. See what happens. This should provide more valuable insights than the simple theoretical RF attenuation of water per ... 4 There are many factors that make BLE low power, and I have attempted to address as many of them as possible. In order to better understand the power consumption differences between Bluetooth classic and BLE, it would helpful to look at some of the differences between the Bluetooth technologies. This would help appreciate the difference in power consumption. ... 4 Firstly you seem to be under the common misunderstanding that the GPS satellites somehow calculate where a GPS receiver is. They don't. The satellites are transmit only systems (ignoring the command and control radio links with their control stations) and a GPS receiver is a receive only system. As user114749 indicated RFID is the closest to what you want ... 4 why not scrap all the obsolete bands and reassign the 1 GHz - 6 GHz range to WiFi? First of all, these bands are not obsolete, there are many uses that might seem outdated, but won't go away easily. Check for example the use of the Ultra high frequency band. Notice also that - yes - the use is country dependent, so if one of these bands have a critical ... 4 The radio spectrum is limited. There are is only a finite range of frequencies over which we can transmit so you if have two people communicate by directly transmitting to each other over two frequencies, no one within the maximum transmission range of either user can use that frequency. If the maximum range of those users is very large, then that means very ... 3 Different materials reflect, absorb, and scatter different wavelengths of light. The ionized layer at the edge of earth's atmosphere happens to reflect a certain range of wavelength while transmitting others. This is due to the physics of the material. The reason you can't use the atmosphere to reflect shorter wavelengths for the purposes of communication,... 3 First, you should link in a reference to the Hata and Ericsson models. I haven't heard of them, and a quick search on Google didn't give anything. Path loss and received signal strength are typically calculated using the Friis Transmission Equation. http://en.wikipedia.org/wiki/Friis_transmission_equation To use this equation you must know the distance ... 3 SC-FDMA is encoded and transmitted from the handset where there are power tradeoffs. This encoding is better than OFDMA for the handset for the following related reasons: Reduces peak to average power ratio Increases efficiency of the power amplifier Increases battery life So at the base station they can employ transmitters that can handle a higher peak ... 3 You may be misunderstanding what "undertakers" actually did in this time period. Even in the 1950s in the UK when I was growing up, in rural areas the local undertaker not only did the carpentry and joinery to make his own coffins, but also did house repairs and general engineering work on farm machinery etc, and quite likely did a bit of furniture making ... 3 Joe and Sue's calls would go to their exchange where the lines were terminated on an automatic exchange. There is (generally) no electronics between their wall socket and the exchange circuits so there was no way of switching calls. It was all invented by a funeral undertaker so it couldn't be that hard - could it? Video links: The Telephone Exchange (... 2 Is there a way to have this device communicate with another device outside of the microwave oven without the microwaves interfering with it? Not with most local wireless communication protocols because they use the same frequency band as a microwave. However on lower power settings the microwave will turn off periodically. That will be your chance to ... 2 The wave propagation speed is only relevant when you start approaching the theoretical limit of that type of wave's ability to transmit information. For an analogy, consider people having a conversation in a room full of air. They're using sound waves to transmit information. The speed at which those waves propagate is the same for every speaker, in that ... 2 Let's assume that you are using OLEDs (organic light emitting diodes) which can emit a photon when charged with an electron. You could build a single molecule pixel (just nip down to the corner store and pick up an electron microscope with atomic manipulator). However the Real challenge is the wiring and insulation. the real question is how are you going to ... 2 First point is that signum is not continuous with the jump at$t=0$. Second because of the absolute value in the integral it has the same$E$and$P$as a constant signal$1$. This means that$E_{sgn}=+\infty$and$P_{sgn}=1\$

2

Generally when you need to scale up a clock you use a PLL (Phase lock loop). A very crude explanation is that you have a voltage controlled oscillator at roughly the required frequency. You divide the output of this down to your reference frequency (a factor of 60 in this case) and then compare it to your reference clock input. The difference between the ...

2

They would be a great hazard to air traffic; The umbilical would be essentially invisible to passing aircraft. In spite of regulations not to fly here or there.

2

You only know something is an "image frequency" because you know what the signal was like before you sampled it and reduced its bandwidth. Do an experiment, either with real hardware or a computer simulation. Use a sampling rate of say 1000/sec and sample analog sine wave signals at 200 Hz and 800 Hz. The sampled data will be identical even though you ...

2

Yes! The logic gates from a RS485/422. Most likely the signal are level shifted. Below is an except form Low power RS-485/RS-422 transceiver ST485B, ST485C datasheet. Below is an another similar part. PROFIBUS Compliant 6kV VDE-Reinforced Isolated RS-485 Transceiver ISL32741E. The example circuit is converting signal 3.3V-5V and 5V-3.3V.

2

This is still done by scammers who want to trick somebody into believing there is something wrong with the internet connection of their PC, and that some malware on their PC can disconnect their phone line permanently. To "prove" the phone is disconnected, they ask the victim to hang up and call them back. They simply leave their own phone off the hook, so ...

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