I have a lot of conference calls in my office where a number of us are clustered around a speaker phone. It is one of those spider shaped Polycom devices and it used to be, that whenever we were on a call, someone’s phone would cause a pulsing like noise on the phone. It still happens today, but not as often and not as badly. You might think that we are getting fewer calls and fewer messages, but that’s not it. So what gives?First, to understand the noise, we must all understand that mostcell phones emit reasonably strong electro-magnetic pulses when signaling for an incoming call or sending data or an SMS message. The wires to the speaker within the phone (or the speaker coil itself) pick this signal up and it comes out of the speaker. It typically only happens when a phone is pretty close to the speaker. This is pretty basic stuff and it wouldn’t make a very interesting blog if it ended here. The key is in the word most. What’s the difference? Why do some cell phones cause more interference than others? Why do some phones not cause any interference at all?
To understand this, we need to note that most interference comes from GSM phones (in the US that would be AT&T and T-Mobile) as opposed to CDMA phones. This is because GSM phones use something called TDMA (Time Division Multiple Access) for their signaling, voice, SMS and 2G data. CDMA phones (in the US that would be Verizon and Sprint) use CDMA (Code Division Multiple Access), a type of spread spectrum for their communication. What’s the difference? Well I won’t go into the details of CDMA vs.TDMA here - that will need to wait for another blog. What I will tell you is that TDMA separates the signal into little time slices, so that the phone will transmit for one piece of time and then be silent for others. On things like the handshake for an incoming call, SMS messages or slow speed data, the transmissions appear to be pulses - a burst of energy at one frequency followed by quiet time and so one. These pulses are picked up by the speaker and come out as noise. In the world of CDMA, the same power is spread over a broader range of frequencies, without the time slicing. Hence the power at any frequency looks more like low level background noise. If it is picked up by the speaker, it probably shows up as very low level static.
Now even this isn’t the end of the story. It turns out that 3G data, the really fast data that AT&T is always boasting about in the ads, is spread spectrum as well. So, your 3G phone, at least when data traffic is concerned, shouldn’t cause problems like its 2G predecessors. Unfortunately, this doesn’t impact voice or SMS. Finally, I recently noticed one more thing that I can’t explain. That is the iPhone seems to cause less noise that some of the counterpart Windows mobile devices. This I don’t know why.
Truchard will be presented the award at the 2014 Golden Mousetrap Awards ceremony during the co-located events Pacific Design & Manufacturing, MD&M West, WestPack, PLASTEC West, Electronics West, ATX West, and AeroCon.
Robots that walk have come a long way from simple barebones walking machines or pairs of legs without an upper body and head. Much of the research these days focuses on making more humanoid robots. But they are not all created equal.
The IEEE Computer Society has named the top 10 trends for 2014. You can expect the convergence of cloud computing and mobile devices, advances in health care data and devices, as well as privacy issues in social media to make the headlines. And 3D printing came out of nowhere to make a big splash.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.