Frequently Asked Questions

Will NFMI work with digital, frequency hopping, or software-programmable radios? Yes. FreeLinc accessories communicate with an adapter that attaches to the accessory interface on your two-way radio. They simply take the mic and speaker data moving in and out of the accessory interface and transfer them wirelessly to the accessory. This happens regardless of radio type - single channel, multi-channel, software definable or programmable, frequency hopping, etc. Additionally, as in the question above, since NFMI technology does not propogate RF waves, it does not affect what the radio is doing, regardless of frequency hopping or other techniques.

Does NFMI technology involve any health issues? No. Magnetic induction transmits extremely low power in the range of about 100 nanowatts (nW) compared to RF technologies in the 1,600,000 nW range. In addition, the use of a low frequency band (10 - 15 MHz) significantly reduces the RF absorption by biological tissue. The U.S. currently has the lowest limit (1.6W/Kg) for what is known as specific absorption rate (SAR). To understand how low magnetic induction power levels compares to this limit, consider that if all the emitted power were concentrated into 1 square mm, the measured SAR would be 16,000 times less than the U.S. limit.

Is NFMI technology incompatible with other electronic devices like GPS systems? Yes. GPS and most other transmitting devices use RF and thus has no effect on our technology and vice-versa.

How do FreeLinc products using NFMI technology ensure that my conversation is secure? There are multiple levels of security built into your FreeLinc product with NFMI. First, the magnetic induction technology assures that the communication stays within a 4 to 6 foot bubble, your personal space. Second, the information that is transmitted is digitally encoded. Third, a security code is generated and saved each time your FreeLinc product is plugged into its charger. No connection will be made unless matching security codes are in both the headset and base.

What is the range of the FreeLinc products that use NFMI? Designers of headsets have converged on 4 to 6 feet as the optimal distance from headset to radio. FreeLinc products are optimized so that the personal communication bubble coincides with that distance. This assures the user of the convenience of a wireless headset while maintaining a communication bubble that provides secure and reliable communications.

How does Near-Field Magnetic Induction (NFMI) work? Magnetic induction technology modulates or changes a weak magnetic field at one device and senses it at another. Magnetic communication is not blocked or reflected by objects, it is free from the interference, nulls and fades that are frequently an issue with RF solutions.

What are the practical differences between RF and NFMI? To best illustrate the difference between RF and NFMI, imagine RF transmitting like a radio beacon while NFMI creates a static bubble of about 4-6 feet in diameter. NFMI transmission is limited to a bubble around your device and not broadcast over long distances like a radio beacon or RF. This optimized transmission minimizes the energy transmitted, and assures that your conversation stays in your voice area. Low cost, low power, high quality of service (QoS) and a secure transmission medium, make magnetic induction the ideal medium for personal wireless space.

What are the technical differences between NFMI and RF wireless communications? Whereas most wireless communication is accomplished by propagating an RF plane wave through free space, near-field magnetic wireless utilizes a non-propagating quasi-static magnetic field. For example, in a typical RF communication system a transmitter couples a modulated RF voltage to an antenna. The antenna in turn generates a modulated RF plane wave (in the far field) which flows through free space while alternately transferring its energy between its electric and magnetic fields. The energy transfer between the fields occurs at the carrier frequency that in many modern mobile devices is in the 900 MHz, 1.9MHz or 2.4 GHz range. A receiving antenna on the remote device receives the energy from the plane wave and converts it into a modulated voltage input to a receiver that extracts the information content. A magnetic wireless system on the other hand does not rely on the flow of energy for communication. Instead the modulated magnetic field generated by a transducer element remains relatively localized around the transmitting device. The quasi-static characteristic of the field is the result of the transducer geometry in combination with the carrier frequency of the transmitter. Information is “coupled” through the medium by sensing the time varying magnetic field using a transducer in the remote receiving device. This is the principle of magnetic induction. While a small amount of RF energy inevitably flows from the transducer, the majority of the energy is contained in the form of a magnetic field. It is this fact that provides for some of the unique advantages of magnetic communication.

How does NFMI power consumption compare to that of RF? With signals designed to propagate only within a 2-meter range, magnetic communication has a huge power and battery advantage (up to 6X) over Bluetooth and other competing RF solutions.

How does NFMI signal reliability compare to that of RF? Unlike RF systems that fade, null, are blocked, or have multi-path signal degradation, magnetic induction is highly accurate and retains communication integrity in the presence of people or obstacles.

How does NFMI frequency performance compare to that of RF? The RF band at 2.4GHz is an extremely ‘crowded’ portion of the radio spectrum, and frequent signal conflicts can be expected. Conversely, MI typically operates in the Industrial, Scientific and Medical band at 13.5 MHz - minimizing both spectrum contention and interference to and from other devices. Magnetic induction communication is performed in a tightly-constrained three dimensional “bubble” surrounding each user, and is inherently more secure than RF while providing 10 to 100X the frequency reuse of RF systems.

Does NFMI work with any mobile phone technology, such as GSM, CDMA, TDMA and others? Yes. Since magnetic induction technology is non-RF, it is not prone to interference from or with other RF technologies and the frequency spectrums used for GPS, PCS, cellular, WLAN and PAN communications. Our wireless magnetic communication works in the presence of CDMA, TDMA, GPS, GPRS, Nextel, DECT, WiFi and Bluetooth, to name a few.

Do the magnetic fields interfere with each other? If you come within 6 feet of another NFMI based headset then you will experience some static or out of range tones. This is easily remedied by either moving away from the headset or bringing your base unit closer to your headset which will then automatically “shrink” your bubble.