Full Fiber optic isolation from Telephone lines

Access Control Systems

Burglar Alarm Systems

Fire Alarm Systems

Video Services Using Phone Lines

Computer Modems

Facsimile Machines

Communicating Copiers

Inter-Active Video Games

Direct TV Phone Lines

Home & Business Telephone Systems

ATM Machines

Operator Consoles

Communicating Medical Devices

Monitoring Devices

Credit Card Readers/Dialers

Point of Sale Terminals

Cordless Telephones

Lightning & Telecommunications

Lightning and communications equipment have been adversaries from the first time men strung copper telegraph wire. From that point on lightning has played a role in the design, installation and operation of communications equipment. Early on it was discovered lightning did not have to strike the wires in order to damage equipment and a strike a mile away could induce dangerous voltage in wires exposed to the electromagnetic field. This effect is described as "EMP", or electromagnetic pulse, and is comparable to the EMP produced by a nuclear blast. While many schemes and techniques have been employed to protect equipment, they are revolving around a few basic principals.

Fuses are used primarily for "sneak current" protection and are very slow to react. Modern electronics will most often fail before the fuse reacts. Fuses are current dependent and not effective for surge protection as a stand-alone device.

A SPARK GAP, breaks down when the voltage across it reaches its turn on point (break over voltage). Gas tubes and carbon blocks are the two most common spark gaps. They conduct to ground or another line when their break over voltage is reached. Spark gap devices are often called shunt devices. Gas tubes are popular with telephone companies because they are moderately effective, low cost and rugged. When they fail, they rarely cause the circuit to fail; they just cease to protect.

Metal Oxide Varistors (MOV) are considered state-of–the-art protection devices and commonly used as lighting surge protection devices. MOVs react much faster than spark gap devices and automatically restore to normal quickly. They work much the same as spark gaps (shunt to ground or another line) in they are a shunt device. They also turn some of the energy into heat in the process of conducting the energy to another line or ground. MOVs handle high amounts of energy, less than spark gaps, but more than diodes and are very popular in AC surge protection. However, they add significant capacitance to communications lines, can fail open or short, leaving the equipment unprotected or requiring a service call.

Diodes are solid state (PN junction devices) and are used for lighting surge protection. They are the fastest of the most commonly used devices. They also have a turn on point and conduct much like a restricter valve. Diodes have the disadvantage of being relatively low energy devices when compared to spark gaps and MOVs.

With all these devices, damage still occurs because for any of these devices to protect, they must be connected to another reference (most commonly ground). This ground connection is the problem as not all grounds are created equal and often the ground wires are disconnected, broken, hooked to PVC pipes, etc. For a ground to be effective it must be both very low resistance and very short. A ground can become part of the problem if it is high in resistance and / or long as it can act as an antenna for induced voltages.

To understand this in "telephone terms", let’s define two terms; 1. Transverse. 2. Longitudinal. To make it easy, transverse voltages are those developed between the "tip" and the "ring" wires. Longitudinal voltages are those developed in both the "tip", "ring" and a third point "ground" common to both the "tip" and "ring" lines. The polarity and level of these voltages are equal. That is the "tip" to longitudinal voltages. They are induced into both wires from the environment and are mostly noise. They are meant to be the same since using unshielded wire for communications requires that these longitudinal voltages cancel each other, reducing noise to a low, usable level. The signal, being transverse, is received clearly, even if the longitudinal voltages are present.