Signals Definition and 434 Threads

hey guys - just a question regarding a systems and signals course: if I've got two disctrete signals: x1[n] and x2[n] if i know both signals are periodic (individually) how do i prove the sum of these signals is periodic? requirement for periodicty (one signal): x[n+N] = x[n] where n...

I am trying to come up with a way to monitor a device that alarms. The signal is open collector: high impedance when not alarm. I would also like to be able to connect this to a computer and monitor and log the alarms when they happen. Any help would be greatly appreciated.

I,m trying to do some bike customization and would like to modify my mirrors to have a set of led sequential turn signals on them. You can buy modulators to do this for you but i imagine all it is just a couple cappacitors and resitors pretty much that's involved. I am not a electrical idiot and...

Hi, I hope this is the right forum. I'm a computer science student and at the moment I'm a little confused with some basic theory regarding signals. I am told that some media (such as fibre optics and other forms of unguided media e.g. microwave) only propagate analogue signals. Yet...

Where in the visual system does one begin to recognize the millions of Colors in teh visual spectrum? Do the retinal cells differentiate between them? Or are generic signals carried to the Color Zones(??V4??/IT) where they are differentiated? How would one convert (256,256,256) pixel colors...

Hi i want to find and read about the return to zeroes and non return to zeroes. What are the differences betwwen them ? Advantages Disadvantages>?

Hi i have noticed that some times we can denote an electromagnetic signal using cos os some timew we can write it in exponential form? Is that true? How can we convert from one type to the other? For example i think that the signal Acos(wt-kr) it can be written to Ae^i(wt-kr) Thx a lot

Hi i am wondering how the diffraction interferes with the signals.. I was reading wikipedia's diffaction artiocle .. bt i can't understand clearly what diffraction causes to an e/m wave.. What i know is that the diffraction is bad some times os some other times is good because we can send waves...

Hi, Can someone help explain why something that has the ability to move faster than c can potentially send a signal backwards in time - thus ruling out superluminal travel. If a 'superluminal' ray starts out at t=0 then even if it does travel faster than light, any information it...

Hi do u have any good articles about signals and modulation... I want to know why we use modulation and how the world would be if no modulation was used at all... Waht arre the types of modulation? What are the differences between them? What are the adgvantages and disadvantages for each...

Ok, admit to absolute naivety in this subject, so please excuse any glaring errors and ignorance in this question :) I have a device which according the specs emits a 0.5 Hz square wave that is bipolar and assymetric. The current ranges from 0 - 1000 mA. Figuring that this was a safe...

Method and Apparatus For Transmitting Signals Faster than Light?? (Based on EPR/QM) Method and Apparatus For Transmitting Signals Faster than Light?? (Based on EPR/QM) Does the following apparatus make sense? Please discuss and let me know where the logic or science is falling short, if...

Hi i am wondering in an electromagnetic signal how times bigger the electonic signal is bigger from the magnetic one... I have also read that becuase the electric signal is bigger the most reveivers ignores the magnetic field and only searchs for the electric signal... Do u know any...

signals...help needed hi, can anyone tell me why a discrete time signal x(n-k) where k>0 is shifted right along the X-axis(the time domain) and x(n+k) is shifted left. should'nt it be the reverse? this is for the graphical notation. but for the notation...

Is there a way to tell PSPICE to graph a signal without having to go to Trace>Add-Trace and selecting the signals each time? If I added a signal and then change a component value slightly and run the simulation, is there a way I can refresh the signal without having to go through the add trace...

Hi let's suppore that an antenna creates two signals... The two signal are received from an other antenna but with a main difference. The one of the two signal is reflected in a surface which means that it will travel bigger distance... The two signals are received with a difference in the...

Hi, the title above is a specific instance of a more general question. I'm basically wondering why the atoms in a wall would prevent visible light from passing through, yet allow both X-rays (which are HIGHER frequency) and radio waves such as 802.11b wireless internet (which are LOWER...

Hi, Here's the question: a) There is a radio telescope that is 1000 feet in diameter. It is claimed that it can detect a signal that lays down on the entire surface of the Earth a power of only one picowatt. What power would be incident on the antenna in this case? It seems to me that...

After I have stripped the filters then one of my filters lost all the signals even the signals of the MW marker. What is wrong? The protocol for stripping is this: Warm the stripping buffer (62,5mM Tris-HCl pH 6.7 and 2% SDS) to 50C and put the filter in it for 30min at Room Temp (RT). Wash...

I have a question about finding the signal energy of a signal? What exactly are you suppose to do when you are given a certain function like x(t)=rect(t) sin(2*pi*t)?

does the brain send out signals or frequencies. I believe i recall hearing about something like beta waves perhaps it was. Someone know of this?

http://xyz.lanl.gov/pdf/gr-qc/0501053 The search for quantum gravity signals jan 2005 an overview of ongoing searches for quantum gravity effects.

Digital and Analogue Signals... When learning about digital and analogue signals, I have been told that a fibre optic cable can be used for digital signals, whilst a copper wire is usual used in the case of anaolgue elctrical signals. My question is could they be used for the other things? Ie -...

Suspending clam eggs in seawater containing 60 mM KCl triggers intracellular changes but if the sea water lacks calcium it prevents the activation by the 60 mM KCl. 1) What does this suggest about the mechanism of KCl activation? I know that the membrane potential is maintained by the K...

Is it possible to measure the voltage, current, frequency of the electrical signals generated by human ‘Brain’? :smile:

Interesting stuff.

AM radio -- please help! Hello, Here is some background info. I don't know if it is all necessary to find a solution but here it is anyway: I am currently living in State College, PA. I would like to be able to listen to an AM radio station broadcasting from Philadelphia, PA...

can AM radio waves pass through glass been than FM radio waves? please explain why/how and how this can be shown in an experiment thx :)

From physics sheet - "all signals (digital a reduction in signal power) as they travel through a system and need amplification at certain intervals." Why is this the case?

I am currently studying an International Baccalaureate Physics course, and I am currently in my first year of study (i.e. I'm 16). As part of this, I am doing a presentation on cellphones; not my decision, but to get to the point: If anyone could refer me to some information detailing which...

I am currently studying an International Baccalaureate Physics course, and I am currently in my first year of study (i.e. I'm 16). As part of this, I am doing a presentation on cellphones; not my decision, but to get to the point: If anyone could refer me to some information detailing which...

This is a pretty basic concept of relativity that used to make sense to me but I have since become a little unclear on the issue. The question is how can one violate the principle of causality simply by broadcasting information that travels faster-than-light?

it has always seemed incredible to me how little power it takes to transmit radio signals over vast distances,i have read about how these signals are self sustaining, i was wondering how long a signal could retain its information, could it go clear across the galaxy?

SETI's search for alien contact includes detecting intelligent analog transmissions and also those carrying sequences of prime numbers signifying life elsewhere in the Galaxy. What is the relative ease with which SETI can discern rational analog vs prime number transmissions? Is it a waste...