Despite the fact that security and alarm cables are highly specialized, the technology that underlies them for the most part has not changed for the better part of a century.

On the one hand, this is fortunate as it means the answers to most of the questions addressed below will be consistent no matter where you look.

So let’s take a look at some of the common questions surrounding security and alarm cables.

What Types of Cable Are Used for Alarm Systems?

The type of cable used to wire alarm systems will depend on the type of system being wired. Common types of security and alarm cables include:

• Siamese cables: Siamese cables consist of a coaxial cable and a power cable that supplies power to the cameras involved in the system.
• Coaxial cables: Typically made of thick braided wire, coaxial cables can carry video signals over longer distances.
• Cat5 and Cat6 cables: Cat5 and Cat6 cables are designed for use with internet protocol systems that can supply both power and high-speed video.
• Twisted pair cables: Typically consisting of thin gauge cables containing only a few conductors, twisted pair cables can be an affordable, low-voltage option for security and alarm system wiring.

There are other types of security and alarm system cables but these are some of the most common.

What Is the Difference Between Plenum and Riser Space?

With respect to fire alarm cables and systems, you might see the word “riser-rated” or RR or “plenum-rated” or PR cable. It is important to understand what these mean as the cables cannot be used interchangeably.

Plenum space is the horizontally oriented space that occurs above a drop ceiling or beneath a raised floor. Although plenum space serves a variety of distinct purposes, one of the main purposes is for the communication and distribution of HVAC ductwork.

Consequently, plenum space is contiguous with the space within a building, and air can circulate between the occupied space and the adjacent plenum space. Therefore, plenum cables are made with self-extinguishing insulation material (typically a low-smoke PVC that does not produce toxic fumes when heated). These cables are used to diminish the risk of fire.

Riser space is the vertical space that occurs between the floors of a building and is used for running conduits and wires, gas and water lines, and more between floors. Riser-rated cable must typically are not as flame-resistant as plenum-rated cable.

Because plenum-rated fire alarm cable is made to a higher standard of flame resistance than riser-rated cable, it is essential that riser-rated cable never be used in place of plenum-rated cable.

Why Are Security and Alarm Cables Typically Rated to Such Low Voltage?

Most security and alarm cables are typically rated to very low voltage (12V, 120V, 300V or some other low voltage) because many of them do not supply power.

Security and alarm cables primarily transmit video or audio signals, or other data signals, between nodes on a system, and often do not power the devices which they service.

In some instances, such as in the case of Siamese cables, they provide both power and signal transmission, but in most cases, the freedom from needing to supply power enables them to work with much lower voltages.

What Types of Insulation Do Security and Alarm Cables Use?

The most common insulation type used by security and alarm cables is polyvinyl chloride or PVC.

Why is PVC used as an insulation material among electrical conductors? For one, it is highly affordable, which itself makes it highly attractive to electrical cable manufacturers.

PVC also has a number of other attributes that make it suitable as an insulator of security and alarm cables. For instance, PVC is suitable for use in a wide range of temperatures, between -55℃ to 105℃, which is a fairly wide operating range.

To keep up with the more stringent demands of plenum-rated fire alarm cables, plenum PVC can be used as an insulative material, to protect against the risk of fire.

In addition to its wide range of operating temperatures, PVC is abrasion-resistant and moisture-resistant and exhibits fair degrees of resistance to gasoline, ozone, acids, and alkaline materials. It is also highly flexible, though not at low temperatures.

While PVC is likely the most common material used for security and alarm cable insulation, other materials, such as PE (polyethylene), PP (polypropylene) and TPE (thermoplastic rubber) may also be used.

What Is Shielding? Why Is It Necessary?

Since security and alarm cables transmit data signals, the integrity of the data they carry is vital to the operation of the system. Sometimes, to protect these signals, security and alarm cables are shielded with an aluminum jacket.

This shielding is necessary for the presence of a high degree of EMI, or electromagnetic interference. EMI can result from natural or manmade causes, and often occurs in proximity to other power lines, as the movement of electrically charged particles creates a magnetic field that can scramble the signals carried.

In these instances in which competing electromagnetic interference can disrupt the integrity of the data carried by the security or alarm system, shielded cables may become necessary.

How Far Can You Run Security or Alarm Wire?

Voltage drop refers to the process by which the electrical potential within a circuit naturally decreases as a result of resistance and distance.

Holding resistance and line voltage consistent (as in the case of an electrical conductor experiencing a fixed electrical potential), the voltage drop will increase with distance. At a certain point, the voltage will drop to the point that your devices will no longer be able to operate.

Voltage drop is dictated by the voltage rating of the cable, the supplied voltage and current, and the length of the cable. Since most security and alarm cables are rated to low voltages and consist of thin AWG conductors, voltage drop is a real risk.

Consult an electrical engineer or a power drop distance chart to ensure that you are using the proper alarm cable to wire a given circuit with respect to supplied power, the input requirements of the devices on the system, and the rating of the cables used.

Additional Questions about Security and Alarm Cable?

Questions about security and alarm wire or cable that we didn’t answer here? Get in touch with us at 800-262-1598 or by email at Sales@EWCSWire.com and we would be happy to help.