Seeking RF immunity

Q: I am a consultant with an account in Miami, FL, that has radio-signal problems. The Mitel 2000SX light system was installed two years ago with new cable (Category 3) for the guest rooms in the hotel. Guests are complaining about hearing radio stations while they are talking on Teledex guest-room telephones. Mitel`s advice was to purchase an adapter for the telephones to eliminate the problem.

Jun 1st, 1998

Q: I am a consultant with an account in Miami, FL, that has radio-signal problems. The Mitel 2000SX light system was installed two years ago with new cable (Category 3) for the guest rooms in the hotel. Guests are complaining about hearing radio stations while they are talking on Teledex guest-room telephones. Mitel`s advice was to purchase an adapter for the telephones to eliminate the problem.

I have run into this problem before, most recently in Columbus, OH, where the problem was related to a high-power radio antenna for a local broadcast station across the street from the hotel. Is it possible that the building cable is picking up the radio signals in Miami, and if so, what would you recommend as a solution or what additional information do I need to solve this problem?

John Mathis

Mathis & Associates

Katy, TX

A: Follow Mitel`s advice: Buy the adapters. Work on tia-631, "Telecommunications Telephone Terminal-Radio Frequency Immunity Requirements for Equipment Having an Acoustic Output," published in 1996, was initiated by the TR-41.7 subcommittee of the Telecommunications Industry Association (Arlington, VA) on behalf of the Federal Communications Commission (fcc--Washington, DC), in response to receiving 25,000 complaints each year on telephone RF interference. Sources of interference included AM and FM broadcasters, licensed amateur operators, and citizens` band transmitters, most of which were operating according to their respective licensing limitations.

The fcc also issued a Notice of Inquiry asking whether telephones should be regulated for RF immunity, in response to which TR-41.7 lobbied hard to convince the fcc to allow manufacturers time to implement tia-631 voluntarily.

Donna Ballast is a communications analyst at The University of Texas at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, The University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: ballast@utexas.edu

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