Jag Venugopal's Blog

February 12, 2010

Keeping In Touch With Walkie-Talkies

Filed under: Digital Living — Jag @ 4:46 pm
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Families are well served by a communications device when they are dispersed over a wide area such as a large mall, amusement park, golf course, or just the great outdoors. Such devices help family members take some time off to pursue their individual interests, while still staying in touch. Examples of such devices are the cell-phone, and the walkie-talkie.

Cell phones are ubiquitous, almost everyone has them, battery life is good, and overall, they are inexpensive. However, they have their own drawbacks:

  • They are expensive to replace if damaged or lost
  • They require proximity to a cell tower to function
  • They still cost money

 Over the last decade, inexpensive, yet efficient walkie talkies have emerged on the marketplace that may serve a family’s communication needs, while mitigating some of the drawbacks of cell phones. Such gadgets are:

  • Inexpensive (they typically run less than $100 per pair)
  • Do not require cellular infrastructure to operate (they work fine in the wilderness)
  • They don’t cost anything to operate (other than the cost of batteries)

Most walkie-talkies sold at electronic retailers come in pairs, in a bubble-pack. They operate on the FRS and GMRS frequency bands. The former is license-free, and the latter needs a license from the FCC. The license costs in the neighborhood of $85, and needs to be renewed every five years (though a perusal of the FCC licensing database for GMRS will reveal that unlicensed use is the norm, and the licensing requirements are almost never enforced. As proof, there are less than 2000 active GMRS licensees for the state of Massachusetts).

 By law, transmissions on the 15 GMRS and 7 FRS frequencies are expected to be clear (i.e. no scrambling or encryption). With 22 channels and a number of users, congestion and interference is very likely in crowded places (where they are most likely to be used). Manufacturers tout “privacy codes”, which can be misunderstood as a feature that makes your conversations private. In fact, what they do is to keep other conversations on the same channel (but without the same privacy code) from being received by you. So, its more a nuisance-avoidance code rather than a privacy code.

 On the positive side, there are a number of GMRS/FRS walkie-talkie manufacturers, and most devices are fully interoperable with each other. Emergency hand-cranked radios also incorporate these walkie-talkies, thus allowing someone stuck or lost to try reaching rescuers without the need for fresh batteries.

 Another kind of walkie-talkie that has been on the market for the last three years is a new twist on the old 900 mHz cordless phone. This proprietary technology (called eXRS) works on the license-free 900 mHz band. A major difference between this technology and FRS/GMRS (other than the different frequencies) is that these radios change their frequencies every 400 milliseconds from a pool of about 50 , in a pseudo-random sequence that can be set by the user.

 eXRS devices solve the privacy problem rather nicely. Unless a potential eavesdropper has fairly sophisticated scanning equipment, it will be difficult to tap into a conversation. This makes it sufficiently safe and private for the family in recreation mode. There is no one that can listen in on private conversations, and no one that can interject their words into a private conversation — both features making the devices much safer for kids.

 Other advantages of eXRS are that no licensing is required, and the technology is scalable to many more concurrent users (the manufacturer claims that 100,000 users can be using the device in a given area without congestion. Even assuming that they have exaggerated by a factor of 10, there is plenty of scalability built in).

 There are two disadvantages of eXRS devices: They come from a single manufacturer, and are not an industry standard. This means that the rapid pace of innovation in the GMRS marketplace may outpace the lone eXRS manufacturer’s resources. For example, the currently available eXRS radios are not as rugged as the most rugged FRS/GMRS sets available. There are no hand-cranked versions available either. Secondly, they don’t help much as an emergency radio — the privacy features get in the way. The same frequency hopping that affords privacy, also prevents rescuers from communicating with someone lost, using this technology.

 With these caveats in place, I would make the following recommendations for a family that wants to stay in touch in the outdoors:

  • Purchase and use a pair of eXRS radios for general communication among dispersed members
  • Those going camping in out-of-the-way places might also want a hand-cranked radio with GMRS to use in emergencies
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