Russ Gundrum
Kingwood, TX
Just wanted to add a few comments to Mark Waller`s article "Grounding and bonding ensure a safe installation" (see September 1995, page 21).
Instead of using modems, opto-isolators or data-port protectors, or replacing copper cable with fiber-optic cabling, I`d like to suggest a less-expensive and more-effective solution to the problem of induced voltages and currents on data lines. And shielded cable isn`t the answer either--as the telephone industry learned years ago.
Neutralizing transformers were developed more than 60 years ago for use on open-wire telephone lines to reduce induced voltages and currents simultaneously. You don`t need to specify an operating threshold for this device because it doesn`t clamp the circuit and shunt it to ground. There is no time delay, because it operates instantaneously, and it is a multi-pair device, so you only need it at one end of the circuit.
In the 1960s, large units were built for critical telecommunications and data circuits serving substations and power plants that might be exposed to thousands of volts. In the 1970s, smaller and less-expensive units were designed to suppress hundreds of volts. Now, I`m waiting for one to be designed for the local area network market to solve an even lower voltage problem. Any takers out there?