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mysterylectricity
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Pocket calculator and transistor radio.
mysterylectricity   4/9/2014 10:09:16 AM
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When I wired my first house at the age of 16 (about 30 years ago) I faced a somewhat similar prolem at some point. My solution was to loosely wrap one end of the wire around an LED pocket calculator. This was guaranteed to inject a good deal of distinctive RF hash in the line. I then traced the wire with a pocket transistor radio. The idea came to me years after I'd spent a little time listening to my "Dataman" calculator/game thinking to itself on the AM band while drifitng off to sleep one night. Not sure how I discovered that phenomenon, except to say that I was so into calculators and transitor radios at the time that it's likely I chanced upon it. Or maybe Forrrest M. Mims III mentioned it somewhere in Radio Electronics or the like. Now your only challenge is to find an LED or VFD calculator!

mhrackin
User Rank
CEO
Re: One wire try a thousand
mhrackin   4/8/2014 3:39:45 PM
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I immediately thought of my cable toner, which EVERY telecom tech or engineer is (or should be) familiar with.  This is a pair of devices: a signal source, with 2-wire output, and a sensor probe with a skinny nose.  Connect the 'hot" (red) wire of the source to the wire in question and the other to any handy ground. Connectivity of the ground to the far end is UNIMPORTANT for this tool!  Go to the other end of the suspect wire with the probe, and see if it picks up the signal. If so, there is continuity; if not, there isn't!  It's also useful for identifying pairs in a multi-pair bundle (its original intended primary use).

bellhop2
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Re: One wire try a thousand
bellhop2   4/8/2014 2:59:30 PM
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Robert Hope-Jones (1859 -1914) had a telephone background. He transfered this technology to the pipe organ. Nowadays, they multiplex everything on to one wire or fiber optic cable. Pipe organs, however, are built today with technologies ranging from mechanical linkages to fiber optics.

MeasurementBlues
User Rank
Blogger
Continuity in Apple cables
MeasurementBlues   4/8/2014 2:41:01 PM
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Bill,

Today I discovered yet another way that fake Apple cables are made. Put an ohmmeter across the USB connector metal shell and the shell of the Apple connector (I use the 30 pin, not the lightning connector). On genuine Apple cables,  the connector shields on both connectors are shorted. Some fakes leave off the internal wire or connection between connectors.

I have a few Dynex charge/sync cables and the connector shields are shorted together. That's clearly the better design and they are only $8 at Best Buy.

I tested a Belkin Apple charge/sync cable. The connector shields are shorted together.

The lack of shielding means no protection from EMI of from emitting EMI. That would make another good test, check eimissions of cables with the connectors chields connected.

Sheepdoll
User Rank
Blogger
Re: One wire try a thousand
Sheepdoll   4/8/2014 1:12:33 PM
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@zeeglen - The air valves are electromagnets.  The cable controls the signal flow from the keyboard to the coils.  A mechanincal, electric or electronic muliplexer called a relay is used to activate ranks of piles called stops.

These can be large instruments, the size of rooms.  Cables are cut when the organs are moved or the building pulled down.  An electromagnetic instrument can have a sizable relay, This looks like a telephone switch exchange.  Same inventor Robert Hope-Jones.

 

MeasurementBlues
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Blogger
Re: One wire try a thousand
MeasurementBlues   4/8/2014 11:32:04 AM
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@tb100

I used a cable toner to identify cables running through my house. There are 9 jacks located through out the house. I'm sure glad I put one on every possible place where a TV might go. We ended up moving the TV a few months after we moved in. I'll I had to do was connect a different cable in the wiring closet. All cables are marked as to their destinations.

zeeglen
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Blogger
Re: One wire try a thousand
zeeglen   4/8/2014 10:44:20 AM
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It is not uncommon for someone to take an axe to the main cable.

@Sheepdoll - just curious, why does a pipe organ have such a cable?  Is it used to activate air valves remotely from a keyboard?  And why would anyone want to take an axe to such a cable?


tb100
User Rank
CEO
Re: One wire try a thousand
tb100   4/7/2014 3:21:49 PM
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Well, you can test 8 cables at a time with a 'cable toner', such as ones made by Aska or Fluke. They are meant for coax, but I don't see why you couldn't use them on other cables, as long as you have a common ground.

Sheepdoll
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Blogger
One wire try a thousand
Sheepdoll   4/7/2014 2:56:33 PM
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I work on pipe organs.

It is not uncommon for someone to take an axe to the main cable.  These are the same as a telephone switch trunk, about 2 inches or 5cm in diameter.  Most modern installations use telephone 50 pair wire code.  The old stuff is cotton covered. 

With over 1000 wires in the bundle, it is usually easier to replace with the color coded stuff.  Otherwise it is toneing the lines out against a common.

I keep thinking there should be some sort of device which puts a different frequency on each line, then tells what connects to what.

stevehgl
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Rookie
single-ended testing
stevehgl   4/7/2014 1:59:50 PM
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We have a network cable tester which (correctly) reports the length of an unterminated cable... slightly different, but hey...

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