Question about Repeaters

[xdectek]

In Mike Meyers Network + (pg. 36), it states that, "A repeater does not function as an amplifier. An amplifier boost signals, flaws and all... A repeater, in contrast, recreates these signals from scratch".

However, in the Sybex Network+ Study Guide (pg. 55), it says that a repeater "amplifies the signals it receives.. ", and "The main downfall of a repeater is that it repeats *everything* it receives on one port, including noise, to other ports". Can someone please tell me which description is correct? Thanks!

John

"Remember you are unique, just like everyone else"

 

[mcconmw]

They are essentially both right. The first is probably a little more technically correct, but the intent of the second is also accurate. The first quote is primarily addressing attenuation. When an analog signal is sent down a wire it begins to attenuate or degrade due to distance, physical flaws in the wire, etc. When a signal is recieved by the repeater it is rebuilt to combat this issue. However, the repeater has no way of telling the difference between noise and true data. To the repeater, your signal is simply an electric current that experiences highs and lows within a range. When it receives noise it rebuilds the signal in terms of attenuation and then repeats it out all other reports.

To rephrase, the primary thing to understand here is the difference between attenuation (the degeneration of a signal) and noise (the introduction of a false signal). I hope this helps.

 

[xdectek]

Thanks for your reply. I agree with you that a repeater just "repeats" what is sees at its input; it doesn't know if a voltage change on the wire is data or just noise. It specifically addresses the issue of lost packets due to signal attenuation on large networks. I'm just a little concerned with Meyer's statement because it seems to imply that a repeater, which he clearly states is *not* functioning as an amplifier (which he states would boost flaws and data), somehow has the ability to "clean up" the input signal as it recreates it from scratch. Sybex very simply states "repeaters amplify signals" (and noise). So I suppose the question as to whether repeaters function as amplifiers seems to depend on your point of view. Just hope this doesn't come up on any cert exams

- John "Remember you are unique, just like everyone else"