We have a machine that “phones home” when there is a fault over an old school phone line using a modem. Everything was peachy until the old analog system got ripped out and a new digital system was installed. The modem still hobbles along, but only one call, and a even then not all of the time.
The system is supposed to call out every five minutes until someone shows up to fix or reset the machine.
I suspect that the modem isn’t hanging up. This was a problem with the original setup and we had to look at several different modems until we found one that would reliably hang up.
So with modems getting scarce, what would be a better way to do this? The machine is “off of the grid” so to speak, and has no plant-wide network connection. This is by intent, as we would like to meet any hackers in person.
I would personally like to use a something along the lines of an Esteem radio myself, but there has to be a way to dial out normally.
I worked in a shop that changed to digital phones and had to change to that companies digital modems that talked directly to their system’s controller.
The fact that your modem works at all once is a surprise.
4G VPN Router and a Red Lion to do the alerts? I say this on the assumption that there is a PLC involved somewhere that the Red Lion could use for the data sources for the alerts and that there is no internet there right now.
I was surprised too, and at the suggestion of my former partner in this project, I increased the delays since she recalled that it seemed to take a lot of time to get the modem to react with the old analog line. I also removed the analog setup code for the .WAV file that we had been loading into the modem and it’s working fine again.
Kira was the one who actually did this part of the project, since as she got up to speed on PLCs, robots, and VB.Net, she took over most of the programming from me and I went back to being retired.
The original thinking was to use something that should be hack-proof. And a modem that doesn’t answer calls, with a program that won’t read the serial port ought to get us pretty close.
It’s working again, but these modems have been known to die on us so I’ll need to come up with something down the road.
