How to Select Cable Assemblies

 Image credit:  Digi-Key Corporation; Lumberg Automation; Phoenix Contact USA 

Cable assemblies are collections of wires or cables banded into a single unit with connectors on at least one end. Cable assemblies are used to connect various types of equipment and instrumentation. The connectors and wire configuration are very specific depending on the application.

When selecting cable assemblies, application and type specifications are important to consider.  Other relevant specifications include gender, shielding and approvals / certifications.

How Cable Assemblies Work

 A cable assembly is identified by the plugs and receptacles that are attached to the ends.  The featured connectors are determined by the application for which the cable assembly was manufactured.  The application may also determines the cable's dimensional and electrical specifications, as well as approvals and certifications.  Suppliers offer cable assemblies for audio / video (A/V), automotive, imaging, radio frequency (RF), and telecommunications applications.  There are also cable assemblies for personal computers (PCs), local area network (LAN) applications, and industrial control and instrumentation systems.  Cordage, patch cords and cable extenders are types of cable assembly which may suit a variety of applications.

Types Of Cable Assemblies

 The various types of cable assembly may be grouped by application.

• Audio / visual (A/V) cables are used to connect audio and video equipment to a computer or display.  DVI, RGB and VGA cables are examples of A/V cables.
• Battery cables are used to connect batteries.
• Computer cables connect hard drives, printers, monitors and other peripheral devices to a computer.  Computer cables include ATA / SATA, IEEE 1394 (FireWire®), IDE / EIDE, KVM, monitor, printer, USB and VGA cables.
• General communication cables provide data transmission and networking between computers, controllers and other devices.  ATM, CANopen, CC-LINK, fibre channel, Fieldbus, parallel, SCSI, and serial cables are all suitable communication links.
• Patch cables (or patch cords) are electrical or optical cables used to connect two or more devices.  Patch cables are available in various lengths and can be used for many different applications, such as panel connection, Ethernet and telecommunications. 
• Telecommunications cables are used to extend or replace cables for telephones and handsets.

Specifications

In addition to application and type, other important cable assembly specifications include connector type, gender, and shielding.

Connector Type 

• BNC connectors are bayonet-style locking connectors.  They are typically used for A/V applications, as well as older devices and third party monitors.

A BNC connector.  Image credit:  CONEC 

•  Centronics® connectors are used with Centronics brand as well as third party peripherals.

A Centronics® connector.  Image credit:  Electro Standards Laboratories 

• DB connectors are used to connect computer peripherals.  They are available with a variety of pin arrangements.

DB9 (9 pin) connectors.  Image credit:  APC by Schneider Electric 

• DIN connectors are designed to adhere to standards from Deutsches Institut fur Normung (DIN), a German national standards body.
• DVI connectors are able to transmit analog (DVI-A), digital (DVI-D) or analog / digital (DVI-I) data.  The DVI-D is the most common connector.

DVI connectors.  Image credit:  Digi-Key Corporation

• FireWire® connectors are available in 4-, 6- or 9-pin configurations. 
• High-speed serial data connection (HSSDC) connectors facilitate high-speed data transmissions.
• Small computer systems interface (SCSI) connectors are intelligent connectors used with computer peripherals.
• RJ connectors are modular connectors used for telecommunications and serial applications.

An RJ-11 connector.  Image credit:  Newark / element14

• USB connectors are available in a various sizes and configurations. 

A USB connector.  Image credit:  Samtec, Inc.

Shielding

Cable assemblies may feature a type of electromagnetic shielding material, which is wrapped around the cable assembly underneath the outer jacket.  Shielding serves to prevent electrical noise from affecting the transmitted signal, and to reduce electromagnetic radiation emission from the cable itself.  Shielding is typically comprised of metal braiding, metal tape or foil braiding.  A shielded cable assembly may also feature a special grounding wire known as a drain wire. 

Cutaway image of a shielded cable.  Image credit:  Tkgd2007

Gender

Cable assembly connectors are available in multiple gender configurations.  Male connectors, sometimes called plugs, consist of a protrusion which fits into the female connector, sometimes known as a receptacle. 

A male (left) and female (right) connector.  Image credit:  Amphenol Alden Products Company

 Common cable assembly configurations include:

• Male-Male:  both ends of the cable assembly terminate in a male connector.
• Male-Female:  the cable assembly features a male connector on one end and a female on the other.

• Female-Female:  both ends of the cable assembly terminate in a female connector.

References

Alpha Wire - Understanding shielded cable

Gore - Impact of material on microwave cable performance

Gore - Selecting the right cable system for your environment

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