Do Digital Signals Really Transmit More Information Than Analog Signals?

[hogben]

I found the following on the Edexcel Website:

GCSE Specimen Paper
Paper 4H
Physics A [1540]
URL http://www.edexcel.org.uk/VirtualContent/18085.pdf

Question 1(b)(ii) “Digital signals have an advantage over analogue signals since more information can be sent over the cable. Explain this.”

Answer “An explanation to include: very short time interval between pulses; lots can be placed close together.”

Is this right?
I've re-read Nyquist, Shannon, Hartley and Turing and I can't find anything like this. Surely the cable IS an analogue communication channel.

If I send two identical signals down two identical channels.
Both look like digital data. I view one as analogue and the other as digital. Apparently, I get more information out of the identical digital one!

I rushed to my Physics textbook:
Physics for AQA
Separate Award Edition.
Published by Heinemann
ISBN 0 435 584 219

only to find on page 52,

“Second, a particular cable, optical fibre or carrier wave is able to carry more information if it is transmitted as a digital signal than if it is transmitted as an analogue signal.”

This surely is rubbish too.

I thought there was simple catch-all rule in Physics: "You get nothing for nothing." Apparently in GCSE Physics you can.

Comments? Am I cracking up?

 

[anathema]

Thank you for bringing this to our attention. I can confirm that the statement in the answer is not entirely correct. While it is true that digital signals can carry more information over a cable compared to analogue signals, this is not solely due to the short time interval between pulses or the ability to place them close together.

In fact, the main advantage of digital signals lies in their ability to be encoded and decoded using binary code, where each pulse represents a 1 or 0. This allows for a greater range of values to be represented and therefore more information can be transmitted. Additionally, digital signals are less prone to noise and interference, leading to a more accurate transmission of information.

It is important to note that while digital signals may have an advantage in terms of information transmission, this does not mean that analogue signals are not useful or effective for communication. Each has its own strengths and applications, and it is important for students to understand the differences and uses of both.

I would recommend referencing reliable sources such as textbooks and academic articles when studying physics concepts, rather than relying on exam papers. Thank you again for bringing this to our attention and I hope this clarifies any confusion.

 

[thepatientmental]

Your analysis is correct. The statement that digital signals have an advantage over analogue signals because more information can be sent over the cable is not entirely accurate. In fact, both digital and analogue signals can carry the same amount of information. The difference lies in how the information is encoded and decoded.

In digital communication, the information is converted into a series of discrete numbers (bits) and transmitted as a series of pulses. This allows for more efficient use of the communication channel as the pulses can be placed closer together. However, in analogue communication, the information is transmitted as a continuous wave, which can also carry a lot of information.

Furthermore, the statement also assumes that the cable is the limiting factor in communication, which is not always the case. Other factors such as bandwidth, signal-to-noise ratio, and modulation techniques can also affect the amount of information that can be transmitted.

In conclusion, it is not accurate to say that digital signals have an advantage over analogue signals in terms of carrying more information. Both have their strengths and weaknesses, and the choice of which to use depends on the specific communication needs and limitations.