Why can't it be used.
What parameter of telephone cable prevents it being used as alarm cable. ?
cable
- Thread starter astra2007
- Start date
What parameter of telephone cable prevents it being used as alarm cable. ?
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Solid cable doesn't work too well in screw terminals and can snap quite easily. It would work, but isn't recommended, and cause stupid intermittent faults on the system.
As for stranded phone cable, aside from the colour differences, I would like to know this too. I thought it would be OK, but judging by what the people on here say, it's a big no no for some reason.
P
Paul_C
Solid-core cable, the same as used for telephone wiring, is used extensively in North America without any big problems. For the screw terminals typically found on door contacts and similar accessories (i.e. conductor wrapped around under screw head) it's much better than stranded.
A
Alarm
Go on then, tell us why?
I can give you a couple of reasons why it should definitely should not, but you go first.
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A
Alarm
I must also note, our other "experts" are not forthcoming here either.
It really makes you think who are actually up to the game so to speak.
It really makes you think who are actually up to the game so to speak.
A solid conductor wrapped around a bolt is more reliable than a stranded conductor.
Stranded conductors need extra care to keep all strands under equal pressure and contact area. Over time strands can move as copper deforms and they can then fall out from under the head of the bolt.
Using a terminal cup washer to hold all the strands under the bolt head makes for a more reliable joint.
http://www.challenge-indfast.co.uk/pr6.htm
Stranded conductors need extra care to keep all strands under equal pressure and contact area. Over time strands can move as copper deforms and they can then fall out from under the head of the bolt.
Using a terminal cup washer to hold all the strands under the bolt head makes for a more reliable joint.
http://www.challenge-indfast.co.uk/pr6.htm
A
Alarm
Was I asked a question there?
Personally?
As i said, still awaiting an answer myself.
Personally?
As i said, still awaiting an answer myself.
The correct way to prepare stranded conductors for screw terminals where low electrical noise connections are required.
http://www.britishtelephones.com/telephone cords/ericsson handset cord small.jpg
The strands are bound in thin tinned copper and then this bound section is formed into an eyelet using cotton thread to bind it in shape.
It is by todays "standard" a very old fashioned method but was very easy for the installer ( where the eyelet had been pre-formed in the factory ) and very reliable over many many years of service.
http://www.britishtelephones.com/telephone cords/ericsson handset cord small.jpg
The strands are bound in thin tinned copper and then this bound section is formed into an eyelet using cotton thread to bind it in shape.
It is by todays "standard" a very old fashioned method but was very easy for the installer ( where the eyelet had been pre-formed in the factory ) and very reliable over many many years of service.
P
Paul_C
For the reason Bernard has already mentioned - Solid provides a much better connection with a wrap-around screw terminal.
P
Paul_C
How is it any harder than working out what is what with any other type of cabling? In either case you need to check to see which color wire has been used for each function.
Aside from the method Bernard outlined, there are cable testers readily available these days which inject various signals at one end of the cable and then use a receiver at the other end to automatically indicate which conductor is which.
But it's possible to do it with nothing more than a simple continuity test if you have to. For example, for a 4-core cable you could do the following:
At one end, link any two conductors together, making sure that the other two are open circuit. Go to the other end, and find the two wires which show continuity. Arbitrarily label them 1 & 2. Link the wire you've labeled 2 to either one of the remaining wires, and call that wire 3. Label the remaining wire as 4. Return to the first end, and find which of the single wires gives you continuity to the two wires you linked together at the start. That single wire must be 3, and the remaining single wire must be 4. Remove the link between what must be 1 & 2, and find which of those two wires shows continuity to 3. That wire must be no. 2, and the other must, of course, be no. 1.
It becomes more involved for a larger number of cores, but it can still be done.
A
Alarm
No it does not.
We are talking about contacts/vipers are we not?
Still awaiting a correct answer.
Many hours of companies testing of different methods of securing conductors into terminals have come up with some basic ideas as being valid.
In the absence of soldering then a cold weld joint is the best option. A properly formed crimped joint will cold weld some of the conductor surface to connector.
The contact area should be gas tight to prevent oxidation occuring in the contact area. ( gas tight = impossible for air / gas / moisture to get between the surfaces in contact )
In joints where cold weld is not possible the conductor material must be robust / rigid enough to not continue to slowly deform under the pressure of the mechanism.
A bundle of round strands in multi-strand conductor has voids between the strands which are spaces into which the metal can deform into The voids also allow air / gas / moisture to permeate into the joint area.
For these reasons it is better that multi-stranded conductors are crimped into a ferrule or other termination with immediate deforming of the round strands into shapes that fit better together thus reducing (ideally eliminating) the voids between them.
IDC punch down connections when properly performed produce a small but adequate area of gas tight contact and may create an area of cold welded joint.
In the absence of soldering then a cold weld joint is the best option. A properly formed crimped joint will cold weld some of the conductor surface to connector.
The contact area should be gas tight to prevent oxidation occuring in the contact area. ( gas tight = impossible for air / gas / moisture to get between the surfaces in contact )
In joints where cold weld is not possible the conductor material must be robust / rigid enough to not continue to slowly deform under the pressure of the mechanism.
A bundle of round strands in multi-strand conductor has voids between the strands which are spaces into which the metal can deform into The voids also allow air / gas / moisture to permeate into the joint area.
For these reasons it is better that multi-stranded conductors are crimped into a ferrule or other termination with immediate deforming of the round strands into shapes that fit better together thus reducing (ideally eliminating) the voids between them.
IDC punch down connections when properly performed produce a small but adequate area of gas tight contact and may create an area of cold welded joint.
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