Very slow SMS delivery

desertnomad

    I have a SwitchBox (https://switchboxcontrol.com/)

     

    This is a box that uses a T-Mobile SIM to control power to remote devices. It is used typically in an aircraft hangar to turn on an engine pre-heater. It works by receiving SMS messages containing commands. Sometime when I send it a command, it responds within a few seconds, and sometimes the message is not delivered for a few hours. This afternoon one message took 4 minutes to be delivered to the box and the next one took two and a half hours. In both cases I can see the credit debited from my pre-paid T-Mobile account immediately.

     

    What is the problem with these long delays when sending an SMS to a T-Mobile device?

      All replies

      • tmo_chris

        Re: Very slow SMS delivery

        Hey there! Thanks for taking the time to post to our community! I have actually never heard of one of these types of devices before. With the billing side of things picking up the message right away, that means that the network definitely saw the message. I am wondering if it could be something going on with the device. Do you have a T-Mobile phone that you can try the SIM card in to see if the delay persists?

        • desertnomad

          Re: Very slow SMS delivery

          I don't have a good way to put the SIM into a phone to test it. It seems pretty random. Yesterday it was being delivered in about 1 minute in the morning but around noon it was taking 25 minutes. I can see when the power is actually switched and at that point the box sends a confirmation SMS. From the time the power actually switches to the time I get the confirmation is about 8 seconds. As far as I know there is never a delay when the box sends a confirmation SMS to my phone.

           

          So, the problem only seems to be the box receiving the message. Once received, the power switches and a confirmation SMS is sent. I am wondering if it could be related to area codes I am in 775 (Reno, NV) but the phone number for the box is in 607 (New York). The box is receiving a cell signal (17 out of 32 strength according the the box). Does the message have to go from my Nevada phone to New York first even though both my phone and the box are receiving a Nevada cell signal?

            • tmo_chris

              Re: Very slow SMS delivery

              I don't think that would cause that much of a delay. I know you said you don't have a good way to test the SIM in another device but this will ultimately be the best way to see if the issue is with the device or network.

            • desertnomad

              Re: Very slow SMS delivery

              I found an old phone that can take the large SIM card used in the device. The problem is that sometimes it takes 1 minute and other times more than an hour so it may take quite a bit of time at my hangar to replicate it. Assuming the same delay happens with the phone too, what could cause that and what is the solution?