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Push-to-Talk Over Your Smartphone

Over the last decade or so a company called Nextel popularized a Motorola technology called iDEN. Other providers around the world also offered this technology, including Telus MIKE in Canada. It offered standard cellular telephone calls, just like everyone else, but it threw in something extra that set it apart from the crowd; it offered a push-to-talk feature.

This feature of the network made it possible to use an iDEN phone as a walkie-talkie with virtually unlimited range. It was quickly adopted by many industries as a substitute for device-to-device 2-way radio, because they could use it just about anywhere and they didn’t have to build their own infrastructure. Even some police forces (notably the Durham Regional Police outside of Toronto) used it as their 2-way radio system for years.

At first iDEN was offered primarily to industry and no attempt was made to market it to the general public. That changed when Nextel spun off a pre-paid division called Boost Mobile. They managed to generate quite a bit of public interest in the idea of PTT and as a result they over-saturated their network in some places, which didn’t go down well with commercial users, who needed a reliable radio service.

In the near future iDEN will mostly disappear from the cellular landscape in many countries and all that will be left are small low-volume networks (as it is fairly inexpensive to license and run a small iDEN system). The rest of the world has moved on to newer technologies centered on data rather than voice. iDEN was only ever capable of very limited data throughput, which topped out at a mind-bogglingly slow 30 kilobits per second. Yes, that’s a mere three one-hundredths of a megabits per second, which seems almost prehistoric next to maximum speeds of 75 to 150 Mbps on some LTE networks.

Even before iDEN’s imminent demise, mobile operators looked to providing the same sort of push-to-talk service over their data networks. This was met with limited success, because until LTE came along the latency on cellular data was too high to provide the same sort of quick response that was achieved on iDEN. Motorola pulled this off by providing PTT as a circuit-switched service rather than a packet-switched service. Latency was never really an issue.

These days however, we have low-latency data networks that are quite capable of providing push-to-talk services with tolerable delay and as such we can enjoy the same services on our existing phones. Some cellular providers offer commercialized PTT services that they charge extra for, but compensate you by offering a guarantee of quality. Most of us wouldn’t think of paying extra for such a feature, but luckily for us this isn’t a problem.

There are quite a few push-to-talk services available that are completely free-of-charge and require nothing more than the installation of a free app on your smartphone. My PTT-of-choice has long been Zello, which is operated as a commercial service for businesses that also offers free use to the general public. Their service is quite reliable (downtime has been minimal in the last year) and offers incredibly good voice quality. It has very short latency on WiFi and LTE connection, and very tolerable latency on 3G networks.

You can use Zello in one of two ways. First you can use if as a walkie-talkie with your friends and family. The cost of talking with someone is very low, because you...



consume only a small amount of data. I use it frequently with my wife, who has a prepaid service and she consumes less than 100 MB per month for everything she does with the phone, including PTT conversations. The second way of using it is in a group conversation. Zello (and many of the other PTT services) offer you the ability to create a group and set who has access. There are countless group discussions you can join in on (like old-fashioned CB radio). You can also create your own private groups to have closed group chats.

I can’t speak for all PTT services, but Zello is available across many platforms. You can find apps for Android, iOS, and Blackberry. They are now offering a beta test service for a Windows Phones version. You can even run Zello on your Windows-based PC. This means you can chat with all your friends, no matter which device they own.

The PC-based software offers a VOX feature, which has led to some rather interesting uses of the service. For example, a number of HAM radio repeaters (especially in the US) use this to “repeat” their repeater over a Zello group channel. The VOX feature of the PC software ensures that it only “transmits” when there is audio present.

In most cases these repeaters are listen-only channels, but in a few cases they allow users who have HAM radio licenses to talk on the Zello channel which then transmits what they say over the air on the HAM repeater. In other words, they can leave their HAM equipment at home and use their smartphones to transmit to other HAMS over the repeater, just as they would have with their radios.

In fact, Zello was in the news just recently, because protesters in Venezuela were using Zello to communicate with one another and to organize their protests. The Venezuelan government blocked access to Zello to prevent protesters from using it, but Zello immediately put out a new version with a workaround for the block.

The above real-world example aside however, many people don’t really get the point of PTT. If you’re going to talk with someone, why not just phone them? To some extent this is a valid point, as not all conversations lend themselves to PTT. However, a phone call is all-consuming. If I call someone, we must concentrate almost solely upon the call to its completion. With PTT we can behave in much the same way we do with texting, which is to reply when we get a moment.

If we’re really busy, this is a useful way to carry on a low-concentration conversation. Additionally, if we need to say something quickly to one of our friends we can speak right out of their smartphone without them even having to pick it up. Add to all the fact that there are never long distance charges no matter where on the face of the Earth the two ends of the conversation are.

PTT is another communication tool that we can use when we find it serves a useful purpose. It doesn’t cost anything to give it a try, except for the small amount of data it uses (which is really not an issue if your phone is on WiFi at the time). You might come away feeling it’s just a novelty, but then again you might end up wondering how you got along without it.

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