Applications Note: Making CTI
Network Cables
This Applications Note describes
how to make your own modular cables for use in connecting modules in the CTI
network.
Overview:
The CTI network employs the same
familiar 4-conductor cables widely used to connect modular telephones. These can be purchased in a variety of
lengths directly from CTI, or from virtually any electronics or home supply
store.
However, making your own modular
cables is remarkably easy, and is a great way to save money when construction
your CTI network. The tools and raw
materials required are very inexpensive, and can be found at any electronics
store. And making your own cables lets
you customize their length to match you layout’s needs, keeping your wiring
neat and clean.
Materials Needed:
The following tools and materials
are all you’ll need. Part numbers and
advertised prices for various suppliers (accurate at the time this app note was
written) are also shown.
Combination modular 4-conductor
modular 6 position/4 conductor “RJ11”
strip and crimp tool phone cable modular
crimp plug (2 per cable)
|
Radio
Shack
|
DigiKey
|
Mouser
|
Modular
Strip/Crimp Tool
|
279.388
($10.49)
|
A9989
($24.48)
|
382-2196
($16.43)
|
4-Conductor
Cable
|
278.367
($14.49/100’)
|
H0041-100
($8.69/100’)
|
172-UL4210
($52.55/1000’)
|
6P4C
RJ11 Crimp Plug
|
279-384
($0.35)
|
A9116
(0.32)
|
154-7623-4
($0.17)
|
Making Cables:
In general, making cables is self-explanatory. After cutting a section of bulk 4-conductor
cable to the desired length, use the stripper portion of the tool to remove a
small amount of the outer plastic sheath from each end of the cable. (Most tools provide a physical “stop” to
ensure the optimal amount of insulation is removed.) Then fully insert each
stripped end of the cable into an RJ11 modular plug, and using the crimp
section of the tool, fasten it permanently in place.
The only aspect of the cable
making process that requires some clarification is the relative orientation of
the RJ11 plugs at each end of the cable.
There are two styles of modular cables: commonly termed “phone” cables and “data”
cables. The CTI network was designed to
use “phone” style cables, since these are universally available in the
U.S as a result of their use in modular telephones. If you buy a modular cable in the U.S. you
can usually rest assured it will be the correct “phone” style
cable. However, users living in
countries that do not employ the modular telephone wiring standard should use
caution. If you buy a ready-made cable
in those countries, there’s a good chance it may be a data cable, which
will not work with CTI.
Telling the difference between
the two types of cables is easy, as shown in the illustrations below. Lay the cable out perfectly flat end-to-end,
with no twists. If the spring clips on the crimp plugs are both on the same
side of the cable, you have a “phone” cable. If the clips are on opposite sides of the
cable, the cable is a “data” cable.
A Modular “Phone”
Cable (side view)
(The correct cable orientation for use with the CTI
network)
A Modular “Data”
Cable (side view)
(The incorrect
cable orientation for use with the CTI network)
For convenience, manufacturers of modular cable provide a
visible and tactile marker on the outer cable sheath (usually a raised ridge
running the length of the cable). Using
this marker as a guide, align the modular plugs so that the spring clips are on
the same side at both ends (which side of the cable you choose doesn’t matter).