Joe: Yes, it has NOM certification for Mexico, and we have a lot of devices that have NOM certification in them. There have also been some changes in regulations. We have new products coming out, so if there's a gap that you're seeing that we're not covering, we have salespeople dedicated to Mexico and in-country distributors. So if there's a certification need that we need to address, definitely just let us know.

Mitch: The specific products they're asking about are the Long Range 868 megahertz module and the 900 megahertz module.

Joe: The 868 is specifically for Europe, so we wouldn't be able to certify that in Mexico, because that's used for cellular technology. But for the Digi XBee 900-megahertz module, yes that has NOM certification.

Joe: Yes, we do have deployments in India. And Digi is very involved in the mining sector and in environments similar to the harsh conditions that John's solution faces in the transit sector. When you go to a mine, it's dusty, it's hot, and often at high elevation. It also can get extremely cold in the nighttime and there’s snow. We do have customers that are building applications, whether it's in mining trucks, or the conveyor belts, or with the disbursements of a lot of chemicals that are being used in a mining environment. So we're definitely familiar with that, and we have folks in the APAC area that could that could help with that.

John: We do support more than one module. We use both a surface mount module, which is typically the 2.4 Gigahertz XBee Zigbee module. And we have an expansion module slot on there so we can slip in any other technology we might need.

The short answer is no, we don't have any problems with interference or with the multiple interfaces. As long as you provide some minimal spacing between the antennas, we have not seen any problems. For example, we're using the 2.4 gigahertz Zigbee alongside the 900 megahertz Long Range modules, or along with the cellular XBee modules. So the short answer is, as long as you follow the basic rules of engineering, you should not have any issues there.

John: That's actually kind of a funny story. The short answer is we don't have problems with range, especially when we look to the third generation, the XBee 3 modules.

We were designing a new product for one of our customers out west, and we were out there late at night doing some data access control designs. We had one module inside of a metal guard shack, essentially trying to monitor vehicles in and out. We wanted to see what kind of range we were getting off of these units.

I foolishly volunteered to take one of these modules and just start walking to see how far I'd go before we started losing signal integrity. So, I’m 50 feet out, and everything looks good. I was using one of the Digi development boards, which is battery powered, so I can see little lights blinking. 50 feet out, it's working fine. 100 feet out, it's working fine. 200 feet, it's working fine. 500 feet out is working fine. 1000 feet out it's working fine.

By this time, I'm on the other side of the facility, on the other side of bus washers, on the other side of rows of buses. I think I got to around 1500 or 1800 feet away from the guard shack where I said, okay, I'm coming back now. So I got back and everyone was laughing because they could still see the signal.

So the short answer is that we don't have range problems, even in the densely packed environments in the garages themselves when all the buses are back, late at night. They’re metal frame buses and all that, so you're definitely not in line-of-sight range, but we easily see 200 to 400 feet of range reliably.

John: No, not really. With these units, I think their transmit power consumption is around 110 milliamps. So, if we were sitting there transmitting all day long, 24/7 with the engine off, then yeah, we might put a strain on the battery at that point. Just sitting there idle, I think their power consumption is couple of milliamps. And they come with several methods of power control, hardware and software. So you can really minimize the power consumption of these modules, put them into sleep mode, or whatever you need to. We don't have any problems draining the batteries at that point.

John: We have never once interfered with one of our customer's Wi-Fi products. Where we would typically see the potential for interference would be for the transit bus or the paratransit bus where they have Wi-Fi for the onboard systems and Wi-Fi for the ridership to use. We've never interfered with any Wi-Fi. Now, Wi-Fi and Zigbee do kind of overlap on a couple of the channels, so there is the potential. About the only time we've ever seen a problem is when we have our Zigbee module mounted, 12 to 24 inches from one of the high-power Wi-Fi transceivers and we're sharing a similar channel.

And we've always been able to get around that by either switching our channel or switching the Wi-Fi channel or just moving the module slightly further away. It's not really interference so much between the signals as it is that the high power output of the Wi-Fi antenna can swamp the receiver of the lower power Zigbee module. But again, we've only encountered that in two places out of the 90 or 100 we put this equipment in, and it was always pretty easy to get around. We just scoot it a little further away. They coexist very well.

Mitch: Okay, I will thank you both for your presentation and for answering our questions.

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