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From what I understand, both of these things inhibit electronic devices from communicating with each other. A scrambler does this by altering the signals sent out by the transmitter device in such a way that corrupts the data the signal is trying to relay.

What about a signal jammer? Does it work the same way? Are both of these devices the same thing?

(Note: I have asked a question on here before that was not related to electrical engineering. If this is another such question, please let me know! I will happily remove it.)

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closed as off-topic by Chetan Bhargava, Daniel Grillo, Leon Heller, JYelton, Matt Young Feb 11 at 16:36

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This question appears to be off-topic because it is not about Electronic Design –  Chetan Bhargava Feb 11 at 4:59
    
@ChetanBhargava I see. Where is the appropriate place to ask a question like this? Should I remove it or is the put on hold thing taking care of it? –  DanielTA Feb 11 at 19:42
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2 Answers 2

up vote 4 down vote accepted

Jammer and Scrambler serve very different purposes.

Jammer generates interference, which inhibits the ability to receive the signal.
Alice transmits a signal for Bob to receive. Oscar transmits a jamming signal, which interferes with the transmission. Bob sees a reduced SNR at his receiver. Bob's ability to receive Alice's signal is suppressed.

Scrambler is similar to encryption of the signal. There's a also a type of device called Descrambler, which converts the signal to an intelligible form. Alice transmits a signal for Bob to receive. Eve wants to eavesdrop on the signal and obtain its content. To prevent eavesdropping, Alice scrambles the signal. By agreement with Alice, Bob has an appropriate descrambler, so he can convert the signal to an intelligible form. Eve doesn't have an agreement with Alice, and she doesn't have an appropriate descrambler. Eve can not obtain the content of the signal.

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But if Eve had a jammer she could try to keep the scrambled message from Alice being correctly received and descrambled by Bob. –  George White Feb 11 at 4:56
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xkcd.com/177 –  Phil Frost Feb 11 at 14:35
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As said in another answer, a scrambler intentionally works on the transmitted signal but, there is another important use. A scrambler will keep the transmitted signal alternating between 1 and 0 (even though the raw data may be high or low for long periods). This sounds trivial but it isn't - there are two benefits: -

  • Data transmitted (scrambled) can be sent over an AC coupled transmission line - there is no dc content that is useful when receiving - this means scrambled data can be modulated onto a carrier or sent through a line coupling transformer or a capacitor.
  • Because there will be many more high and low transitions (compared to the raw data), the receiver circuit is always being "clocked" and can therefore use simple clock recovery techniques to keep a free-running (but adjustable) oscillator synchronized to the data. This is usually why this type of data transmission system is called "synchronous".

A de-scrambling circuit is almost identical to a scrambling circuit and there are many different types but I suspect a lot of them rely on D type flip-flops and exclusive OR gates for impressing a pseudo-random carrier onto the raw data.

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Jamming and scrambling are as different as chalk and cheese.

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