Switchbox not working

[murphey]

To start - Phillip's support has been outstanding, but we're both baffled at this point. He believes the problem is TMobile 2G coverage. At this point, I don't agree but am willing to accept it once I investigate all possible options.

Anyone here familiar with the GSM switches and wireless phone calls? Remember, I only do software and really weak on networks (databases, large system design, etc).

1) When I call a wireless number, and it goes to voice mail, am I leaving a message on the actual phone's internal memory, or on the phone company's server?
If I use the phone to get my messages, am I connecting to the server or just getting the messages off the phone?

Update....the unit is unplugged but I can still get the voicemail message, so it's a company server, not the phone. Ignore this question.

But calling voice is also supposed to trigger the unit.

2) Got a Switchbox at the hangar to turn on the engine heater the night before I want to fly. I've had it for years and it's great. It has a wireless phone integrated on the board with the switch. It can be triggered by either calling the unit or sending an SMS message. The last time it worked was Nov 30, 2018. Since then nothing has worked. Followed Phillip's suggestion to "reboot" (remove the SIM card then reinsert it. Worked in the past but not now.)
(next idea - head over to the TMobile shop around the corner, get a new SIM card and have it re-assigned to the original phone number. Nope)

Phil sent me another unit and have the same problem.

1) calling voicemail - it answers but does not trigger the switch (hence question #1)
a) called from home - CenturyLink POTS
b) called from cell phone, AT&T
2) sending an SMS does not work.
a) from my cell phone
b) from TextFree app on my tablet using wi-fi
c) from TextFree app on my tablet using cell (AT&T)
3) Unit it powered on (red lights blink)

The unit is on T-Mobile 2G, which has worked at the hangar for years. I brought the unit home and set it up, thinking that the coverage has changed. Nope, same problems at home.

The cell (SMS and voice) have worked in the past with no problems.
The tablet (SMS) has worked in the past.
The POTS has worked in the past.
Until Dec 1.

I can send SMS from tablet to my cell phone.
I can send an SMS from my cell to the tablet app, no problem.

Phillip is baffled, as am I. The possibility of 2 units, built years apart, failing the same way is unlikely (but not impossible).

Anyone got any ideas or suggestions? I really hate to move to AT&T for the switch (4G) because

• the unit is more expensive and
• every SMS is 25 cents where TMobile is 10 cents (and I have $60 credit on that line).

I should point out that T-Mobile Tier 2 is clueless. Altho once I explained about the switch, the tech was fascinated and wants to learn more. I explained I use the unit to turn on a heater at a garage/storeroom 30 miles away (all true) so that I can go work on my father's 1957 Chevy that my cousin and I are restoring.

I hate to think that as of Dec 1, that AT&T and TM aren't playing well together.

 

[SkyHog]

Can you take the SIM card and put it into a cheap prepaid T-Mobile phone? That will allow you to determine whether the line is provisioned (it will get signal and receive calls)

If that passes, the issue is with the switch.

 

[Eric Stoltz]

https://orion.freeus.com/coverage-map.aspx might help, but I doubt it is up to date.

Tmob is reducing their 2G drastically I read and hear. I had a similar problem with a different device. I changed to a 4G gizmo and voila. Unless one is a wireless parking meter, or an automated soda machine in a gov't office, we're going to have a bad time with 2G. Tmob is deferring it's sunset on 2G until 2020, but they have a lot of parking meters out there speaking to them, I guess. I hear that Tmob is also not putting in very much maint on the 2G structure either, especially if it is in the way of their proposed 600MGHz (5G) development (coming from an IBEW guy that works on this stuff). No rhyme or reason why coverage works here or there unless you're climbing towers pulling the old junk out.

Understanding the frustration, but 2G is dead, just like cd's. I enjoy a good troubleshooting gig as much as the next guy - especially when it comes to something like bootstrapping an 8 track to a bluetooth controller...but I digress. There are so many variables to the problem, and a simple solution that will most likely work is a technology upgrade. My SIM costs me $80 a year, uninterrupted service. So, with the amount I use the switch, it costs me about $20 a month, or 5 bucks every time I want to show off to myself and have warm oil an hour before I want to go fly. So yeah, a preheater switch is kinda like a lifted truck that never sees mud, imho.