Path: utzoo!attcan!uunet!super!udel!gatech!uflorida!mailrus!ames!pasteur!ucbvax!DSUNX1.DSRD.ORNL.GOV!wnn
From: wnn@DSUNX1.DSRD.ORNL.GOV (W. N. Naegeli)
Newsgroups: comp.protocols.appletalk
Subject: Re:  AppleTalk noise problems
Message-ID: <8809262222.AA00284@dsunx1>
Date: 26 Sep 88 22:22:24 GMT
Sender: uucp@super.ORG
Organization: The Internet
Lines: 22

The Tops Repeater will not help you with noise. It is only useful in situations
where signal strength is insufficient to be picked up by all nodes on a
network with a large effective length. The repeater is simply an amplifier
and as such, it unfortunately also amplifies noise.  If noise is really
your problem you may be worse off with a Tops Repeater.
By contrast, the Farallon StarController does not merely amplify the signal
but has its own receivers and transmitters and reconstitutes the signal.
It will effectively deal with both noise and weak signals, but its cost
is fairly steep if you need only two of its twelve ports. I understand
that the Farallon NetRelay that has recently been announced with a list
price of $500, but is not yet shipping, if I am right, essentially is a
similar solution but has only two (or three?) ports and cannot be controlled
through network management software like the StarController.  It may just
be what you need.
An ohmmeter can reveal the grossest of network problems, but it cannot
detect noise or reflections. With the ohmmeter you can test for continuity
and whether network resistance is in the tolerable range. With a Voltmeter
you can also test for shorting to other (telephone) circuits and induced
currents (both AC and DC measurements should be zero when all devices are
disconnected from the net). To detect and pinpoint noise and reflections
however, you need more advanced instruments, such as storage scopes with
high resolution for timing signals and reflections.