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In our post, Simplify Your Data Management Solution, we addressed the need for separate cable channels for video and data to mitigate signal interference. Another signal interference risk to your dispatch center communications system may come from unintentional radio frequency contamination. Here’s what you should know.


What are radio frequency (RF) devices?

Radio frequency devices are office appliances that omit a radio frequency that uses or interferes with radio channel use. There are three categories of RF devices: intentional radiators, incidental radiators and unintentional radiators. The team over at National Association for Amateur Radio shares these definitions from FCC Title 47, Part 15:

Intentional radiator: § 15.3 (o) Intentional radiator. A device that intentionally generates and emits radio frequency energy by radiation or induction. This term generally means "radio transmitter." Examples are cordless telephones, baby monitors or garage-door openers.
Incidental radiator: § 15.3 (n) Incidental radiator. A device that generates radio frequency energy during the course of its operation although the device is not intentionally designed to generate or emit radio frequency energy. Examples of incidental radiators are dc motors, mechanical light switches, etc.
Unintentional radiator: § 15.3 (z) Unintentional radiator. A device that intentionally generates radio frequency energy for use within the device, or that sends radio frequency signals by conduction to associated equipment via connecting wiring, but which is not intended to emit RF energy by radiation or induction. Examples include computer systems and superheterodyne receivers.

The radio frequency spectrum chart there are many dedicated user groups. As you may know. there is concern that we are running out of radio frequency space to support our growing communications networks. Unintended contamination adds service disruption risk.

redio january_2016_spectrum_wall_chart

How does radio interference affect PSAP communications?

First, you should know that there is misinformation about RF signal risk. Some people contend that RF signals are so small that it’s not likely to cause harmful interference; that is simply not the case. Title 47, Part 15 was written specifically to protect one neighbor’s television reception from another neighbor’s video game. In a PSAP, where operational communication via screen, telephone and radio is a must, an RF check should be part of the systems check protocol. This example illustrates the unintended consequence of an incomplete RF risk assessment:


The Phonex Corporation manufactured wireless modem jacks that operated at a very high frequency. These units were installed by the thousands and the resulting compounded “noise” disrupted certain radio frequencies. As a result, radio users could not access certain channels. Although Phonex addressed the issue right away, problems reoccurred over a year later and it is suspected numerous cases were unreported.

You can imagine the problem this type of interference could cause at your PSAP if frequency access was disrupted.

Vendor partners in the PSAP community who specialize in radio equipment and computer hardware are tuned into the subtleties of RF interference and their products are tested and certified accordingly. What about “non-electronic” items in your PSAP that have electronic components - like height-adjustable furniture or technology furniture that houses heaters and fans?


Is my dispatch furniture a RF device?

In short, the answer is yes. Dispatch furniture is classified as a Class A digital device. A Class A device is any digital device, appliance or unit that is marketed for use in a commercial, industrial, or business environment and contains digital components. The RF interference potential from dispatch furniture is worth noting because interference from unintentional radiators can build up quickly causing signal interference that disrupts communications relay, regionally and nationally.

How do I know if my dispatcher desks are RF safe?

The risk of frequency interference from your furniture is low. And if you have not experienced radio frequency disruption during the lifetime of your furniture, the systems are likely clear. You might find your dispatch desks are labeled Title 47 compliant. In the case of Watson's Mercury consoles, the user manual contains compliance notes. You can also ask your manufacturer to confirm their product meets unintentional radiator standards.

While risk is low, technology continues to change. If you are planning technology or furniture replacement, or designing a new center it is a good time to revisit RF risk with your facilities and tech teams.

RF Interference help from the FCC

Federal Communications Commission (FCC) Title 47, Part 15, is a portion of Title 47 of the Code of Federal Regulations (CFR), that regulates radio frequency (RF) devices. Moreover, Part 15 also sets out the technical conditions for both “unintentional radiators” and “incidental radiators.”

FCC approval standards recommend manufacturers verify products are Title 47, Part 15 compliant before the products are sold in the United States. This guarantees that no undue interference or hazards will harm users. Nearly every electronic device sold within the United States emanates unintentional emissions, and are reviewed to comply with Part 15. Depending on the type of device involved, manufacturer-initiated test results are kept on file or sent to the FCC.


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