We went through the same thing at our hotels last year, so here is what I learned (I’m not an engineer, so this is the manager version).

Edge is software on the licensed gateway. It reads your Modbus devices on site, and each meter or controller shows up in Hermetry as its own child device. The gateway dials out over TLS, nothing on your site has to accept incoming connections.

If the broadband drops, licensed gateways can keep the readings locally and send them when the link is back. Each reading carries the time it was taken, so the history fills in at the right place. How much it can hold depends on the model, so ask for the figure for your model before you rely on it. Our integrator had to check that for us.

What surprised me was that alarm rules and flows run in Hermetry, on the cloud side, and the box only reads and buffers. So during an outage nobody gets an alarm e-mail, and when the backlog arrives the alarm rules look at the late readings by their own rules. Anything that must stop a press in a fault stays in the PLC or the controller, never in the cloud. Our maintenance lead was happy once he heard that.

The page that settled it for us: Licensed gateways and Hermetry Edge

I’m not an engineer, but this happened to us last year, so here’s what I learned the expensive way.

We bought 12 leak sensors for our hotels from a small vendor, LTE-M, certified module, all reporting to Hermetry. Three months in, all 12 went offline on the same morning. I only noticed because the Device offline alarms fired for every one of them within ten minutes, before breakfast. The vendor spent a week on it. It turned out the operator had started rejecting devices whose IMEI range (the first 8 digits, the TAC) wasn’t registered with them as an approved device. The module had its approvals, but nobody had ever registered the finished sensor.

What fixed it: the vendor went through the operator’s device approval, which for a product built on a certified module was mostly paperwork plus a short field test. Our TAC got added and the sensors came back the next day with no changes on our side.

So for your 300 trackers, I’d call the operator now, before the build, ask what their approval looks like for a product on a certified module, and get your TAC registered. And set up a Device offline rule on the tracker profile. Your trackers wake every 30 minutes over HTTPS, so I’d set the profile to Recent message with something like 1,800 s times 2 and a short offline delay on top, so you hear about a block the same morning.