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Wireless Accessories

Wireless accessories have come a long way since 2002 when Motorola created the first wireless accessory device for Motorola two-way radios. Using Bluetooth Wireless Technology, Motorola’s designers developed a remote microphone that enables Motorola two-way radio users to work in a cord-free environment.

The microphone communicates to a Motorola two-way radio through an adapter equipped with Bluetooth Wireless Technology and an adapter-capable battery on the radio. Once the user turns on the two-way radio, the adapter and wireless remote speaker microphone use Bluetooth Wireless Technology to link to each other upon power-up.

This technology is based on a radio link (2.402-2.480 GHz) that offers fast and reliable voice and data transmissions. Bluetooth is designed to be fully functional even in noisy radio frequency (RF) environments, and voice transmissions are audible even under severe conditions.

Bluetooth takes small-area networking to the next level by removing the need for user intervention and keeping transmission power extremely low to save battery power. And each transmission signal to and from your cell phone consumes just 1 milliwatt of power, so your cell phone charge is virtually unaffected by all of this activity.


So, why Bluetooth? Bluetooth is wireless, inexpensive and automatic. There are other ways to get around using wires, including infrared (IR) communication. Infrared refers to light waves of a lower frequency than human eyes can receive and interpret. Infrared is used in most television remote control systems. Infrared communications are fairly reliable and don’t cost very much to build into a device, but there are a couple of drawbacks.

First, infrared is a “line of sight” technology, so you have to point the device at the television or DVD player to make things happen. The second drawback is that infrared is almost always a “one-to-one” technology. You can send data between your desktop computer and your laptop, but not your laptop computer and your PDA at the same time.

Bluetooth is designed to get around the problems that come with infrared systems. The older Bluetooth 1.0 standard has a maximum transfer speed of 1 megabit per second (Mbps), while Bluetooth 2.0 can manage up to 3 Mbps. Bluetooth 2.0 is backward-compatible with 1.0 devices.

Interference with other wireless devices is always a problem, but it is especially of concern for public safety. One of the ways Bluetooth devices avoid interfering with other systems is by sending out very weak signals of about 1 milliwatt. By comparison, the most powerful cell phones can transmit a signal of 3 watts. The low power limits the range of a Bluetooth device to about 10 meters (32 feet), cutting the chances of interference.

Even with the low power, Bluetooth doesn’t require line of sight between communicating devices. The walls in a building won’t stop a Bluetooth signal, making the standard useful for controlling several devices in different locations. Bluetooth can connect up to eight devices simultaneously. With all of those devices in the same 30-foot radius, you might think they would interfere with one another, but it’s unlikely.

Bluetooth uses a technique called spread-spectrum frequency hopping (SSFH) that makes it rare for more than one device to be transmitting on the same frequency at the same time. With SSFH, a device will use 79 individual, randomly chosen frequencies within a designated range, changing from one to another on a regular basis. In the case of Bluetooth, the transmitters change frequencies 1,600 times every second, meaning that more devices can make full use of a limited slice of the radio spectrum.

Because every Bluetooth transmitter uses spread-spectrum transmitting automatically, it’s unlikely that two transmitters will be on the same frequency at the same time. This same technique minimizes the risk that other portable devices will disrupt Bluetooth devices, because any interference on a particular frequency will last only a tiny fraction of a second.

In law enforcement, security is always a concern. Devices can easily grab radio waves out of the air, so people who send sensitive information over a wireless connection need to take precautions to make sure those signals aren’t intercepted. Bluetooth technology is no different.

It is wireless and therefore it is susceptible to spying and remote access, just like WiFi is susceptible if the network isn’t secure. With Bluetooth though, the automatic nature of the connection, which is a huge benefit in terms of time and effort, is also a benefit to people looking to steal your data without your permission.

Bluetooth offers several security modes, and device manufacturers determine which mode to include in a Bluetooth-enabled gadget. For example, as more land mobile radio manufacturers add Bluetooth, it will require some coordination to ensure the radios will communicate with matching Bluetooth accessories.

In almost all cases, Bluetooth users can establish “trusted devices” that can exchange data without asking permission. When any other device tries to establish a connection to the user’s gadget, the user has to decide to allow it. Service-level security and device-level security work together to protect Bluetooth devices from unauthorized data transmission.

Security methods include authorization and identification procedures that limit the use of Bluetooth services to the registered user and require that users make a conscious decision to open a file or accept a data transfer. As long as these measures are enabled on the user’s phone or other device, unauthorized access is unlikely. A user can also simply switch his Bluetooth mode to “non-discoverable” and avoid connecting with other Bluetooth devices entirely.

In public safety applications, manufacturers typically secure their wireless accessories to their proprietary devices to maintain a robust connection without risk of interference. The exchange of a security key upon discovery of the Bluetooth device is often the most common method of securing a connection.


Motorola has taken these issues into account and recently offered a new Bluetooth wireless speaker mic that is integral to the design of the radio. Motorola strongly believes that aftermarket add-on accessories are good, but sometimes if the accessory isn’t designed as part of the radio from the ground up, then critical radio functionality can be lost. Motorola provides a complete integrated solution where the radio is the master of the devices, and this isn’t always the case with a third party aftermarket solution.

The Motorola APX700 series, multi-band radio is Motorola’s fourth generation P25 compliant offering with integrated GPS for outdoor location tracking. Designed with mission-critical technology, the radio is designed with integral Bluetooth to enable a new Motorola wireless microphone. Expected to be available in late-2010, this new Motorola wireless microphone is waterproof to the IP54 standard and is designed to allow water to run right out when being used in extremely wet conditions.


FreeLinc has taken a different approach to wireless police radio communications with its own version of the wireless microphone that does not use Bluetooth technology. The FreeMic 200 is your typical shoulder microphone free from the hazards of the heavy black cords and cables! Without the cords and cables, officers can perform their duties without the aggravation of getting hung up, caught up or grabbed by their cord.

Each FreeMic 200 has an audio outlet to allow the user to keep incoming traffic confidential and maintain cover by silencing the FreeMic’s outbound speaker. A single charge will give the user up to 50 hours of talk time. FreeLinc’s patented Near Field Magnetic Induction technology (NFMI) surrounds each user in a communication “bubble.”

NFMI is a short range, wireless, physical layer that communicates by coupling a tight, lower power, non-propagating magnetic field between devices. The concept is for a transmitter coil in one device to modulate a magnetic field, which is measured by means of a receiving coil in another device. By establishing a link between the FreeMic 200 and FreeLinc radio adapter, communications are securely transmitted from the radio adapter to the FreeMic 200 without the use of wires, cables or cords.

The FreeLinc devices do not need to compete for frequency allocation with other RF devices. The well-defined communication bubble of magnetic-field energy allows for a large number of FreeLinc NFMI systems to be co-located while operating on the same frequency. The rugged design of the FreeMic 200 holds up to everyday duties in every assignment.

Design, coupled with the patented technology, keeps you absolutely safe from all hazards and stresses associated with the cables, cords and wires. The FreeMic 200 is a powerful mic with a high-quality speaker, 2.5mm Earpiece Jack, LED Status Indicator, Volume Control, solid feel Push-to-Talk response, Rubberized Grip and Heavy-duty Spring Clip.

FreeLinc has also realized that not everyone in law enforcement needs to use an exterior radio microphone and often a much lower profile is more appropriate. FreeMotion 100 is the perfect communication device when discretion is required. The sleek, contemporary design of the FreeMotion 100 integrates function with form, allowing you to blend in a crowd while maintaining critical communication.

Each unit comes with an assortment of ergonomically designed ear buds and ear wires to provide you with the most secure, comfortable fit combination. Once fully charged, the FreeMotion 100 will give you up to 20 hours of continuous talk time. The FreeMotion 100 uses the same NFMI technology as the FreeMic 200, keeping your communication safe from interception and interference.

Whether working surveillance, security, or executive protection, the FreeMotion 100 allows you to maintain observation and communicate safely and securely from wires, cables and cords. The FreeMotion 100 has standard features like volume control, a powerful ear microphone, tactile push-to-talk, and an on/off switch along with a charging dock.

Most officers want the radio microphone on the exterior of their uniform for best possible audio. This often creates an issue with weather where snow or rain can get into the speaker and seriously degrade the audio quality. So, when considering what to purchase, ask yourself some questions. Is the speaker diaphragm paper or a water resistant material? Are there drain holes?

The FreeMic and FreeMotion are both extremely water and weather resistant. There are openings on both devices; however, they are not considered “drain holes.” When looking at reusing this type of equipment, sanitary considerations of ear inserts must be taken into account, so consider replacement rubber ear inserts. Are they available and how much? FreeLinc offers replacements on the ear gels and ear hooks, and pricing is between $8 and $12.


PRYME Radio Products is a leading manufacturer of high quality products for professional users of two-way radios. Their products serve many markets including public safety, police, fire, emergency services, tactical and HazMat professionals, as well as industrial, commercial, hospitality and entertainment markets. Recently, PRYME announced the introduction of a wide variety of new products, including its GPSMIC™ Speaker Microphones, which enable the location of users in the field via GPS.

PRYME’s complete line of professional two-way radio audio accessories are compatible with virtually every two-way radio platform. The PRYMEBLU Wireless Adapter allows you to use a Bluetooth headset with your Motorola XTS series, HT1000, PR1500, and EF Johnson 5100 series two-way radios. The adapter also pairs easily with thousands of off-the-shelf Bluetooth headsets.

If used with a headset that supports multiple pairings, the PRYMEBLU Adapter enables operation of both your cellular phone and two-way radio with the same headset. The accessory jack also allows you to connect any PRYME QuickDisconnect series wired audio accessory, such as a remote push-to-talk or lapel microphone, in combination with the wireless headset.

Several push-to-talk options are available, for instance, using the PTT button on the PRYMEBLU adapter to initiate transmissions, or using an optional PRYME QuickDisconnect wired audio accessory such as a PTT-5. RX and TX audio is automatically routed to the two-way radio or to the appropriate wireless or wired audio accessory—depending on what accessories are connected to the PRYMEBLU adapter device. This adapter is powered by the radio so no batteries or charging is required.

It also has a very easy pairing process and remembers paired connections to the wireless headsets even if they are powered off or removed from the two-way radio. To ensure complete user feedback when connecting the devices, a status LED indicates connection to a compatible wireless accessory. PRYME has an entire selection of Bluetooth devices that can be used with the PRYMEBLU adapter, so check out its Web site for compatibility and additional accessories.

Other Considerations

Whether or not your agency uses the traditional wired shoulder microphone or a wireless microphone, both should allow for a 3.5mm stereo jack cable from the radio head, up or over the officer’s shirt, and up to his collar, where a curly cord “pigtail” sound tube emerges, anchored by a small clip on the fabric of the shirt collar. This is where the major benefit of the wireless microphone is realized with the officer not having to deal with feeding that curly cord through various layers of clothing to get the microphone head out to the exterior layer.

Best practices still require that the officer use an “ear kit or ear piece,” which is usually a plastic tube engineered to transmit sound into the ear. The sound tube earpiece is often bundled by a mic and transmit switch on separate cables. The mic and switch can lead to the officer’s shirt cuff or can be secured under the shirt in the chest area.

When looking to get these earpieces fitted for the ear, proper sizing of the silicone earpiece is critical. A badly fitted earpiece will irritate and inflame the ear canal. Most vendors offer multiple earpieces of various sizes and designs, but the best solution is a custom-molded earpiece that is issued to each officer as a personal piece of the kit. An audiologist can make these from $75 to $125.

Consider also that some wireless headsets require their own self-contained power source as not all take their power from the radio, and their “talk time” is dependent on how long that power lasts. The batteries in them are sometimes not replaced quickly in a field repair or exchange, so when they die, either the headset has to be sent back to a technician or, worst case, to the manufacturer.

Remember that with all of these solutions, it is of paramount importance to assure that the wireless accessory has an interface that works with your agency’s portable radios. When making inquiries, have the precise make and model of the radios you use available for the vendor. Then test them in the field and not at a desk. There is no better way to confirm functionality than to have a front line officer test the equipment.

Sergeant Brad Brewer is a 22-year member of the Vancouver Police Department. He sits on the Ford Police Advisory Board and regularly gives presentations at law enforcement conferences on mobile computing, wireless technology and police vehicle ergonomics. He can be reached at

Photo credit: Derek Cain

Published in Law and Order, Mar 2010

Rating : Not Yet Rated

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