listen for massages

I have 'old' original Delorme Explorer.

I can operate it with tracking OFF.

I can set an interval of listening for mew messages to let say 10min

On the display of the check messages icon it says listening for new messages, next listen 12.23 and there is down counter running and saying how many min it takes to next listen.

The device is outside, I have sent message to it (from portal) but after hours it still does not receive anything.

If I go to to push the check now, I will receive the message.

What exactly I have to set up with the listen for messages to actually also receive a message when no active mail check and no tracking is going on?

Does this listen have any function at all?

  • I'm going by memory here because I no longer have an active legacy device.

    In the beginning (when the number of iR devices in the world was small), transmission and "listens" at the device were synchronized. Devices listened at intervals (20 minutes sticks in my head). Based on IMEI, different devices listened at different times. For example, your device might listen at 17, 37 and 57 minutes past the hour, while mine might listen at 10, 30 and 50 minutes past. These were passive listens - radio on and listening, but not actively asking the Iridium network if there was traffic waiting. The messages were timed to be "broadcast" by the appropriate Iridium satellite when the target device was listening. This was inherently unreliable for a number of reasons, including the fact that the device might not be on, might not have a good sky view, etc. at the appointed time. In addition, there was no "feedback" to the device - if the device didn't see a message, it might be because there was no message waiting. But it might also be that the device had a poor sky view.

    Eventually, this was replaced by a combination of passive listens and active checks. Passive listens behave (mostly) like the original scheme, but without the timed synchronization of send and listen. (There is also a special "ring" message involved in this, but it's not worth discussing in detail.) This is still unreliable to the point of being useless. The active check actually interrogates the Iridium network to see if there are messages waiting. If so, the device retrieves them. If not, the device knows that there is nothing waiting.

    Note that passive listens don't consume a lot of power since they involve only the receiver. Active listens involve transmission and consume a lot more power. This is compounded by the fact that the active listen will retry if it does not receive an acknowledgement to its query. Can be a real power hog in poor conditions.

    On newer devices, active checks occur at power on, whenever the device sends anything (sent track point, message, or whatever), once an hour, and on demand. After sending a message, there is also a 10-minute interval of more frequent active checks in order to facilitate "conversational" message exchange.

    I am not sure how this carries back to the original SE and Explorer models. Based on you description of the result, I would guess that the "listen interval" control passive listens. And that "check now" is an active listen. I also do not know if these older devices do active listens hourly, in conjunction with sends, or anything else.

  • Many thanks for the elaborate answer, nice to meet someone who is so deeply involved in the subject as you.

    It is confusing really.

    I know about broadcast msg, this was used by the iridium pagers. Not sure if they still exist, but as far as I remember abt 2 years ago this was still in operation. This did work indeed, provided open sky and the usual radio conditions being OK.

    Ring msg, yes this must be the thing Iridium phones use as alert?

    I am kind of admin of an enterprise account with abt 150 of those Delorme Explorer, those are the little bit squere and hard plastic devices, so not the 'rubber' Explorer. And *one* Mini.

    Now I am not sure, is the way I can receive something by the listen to messages no more operational?

    As I earlier never used the device just for communication, I did never bother abt those functions. Now some users have asked how to set all up to get msg and safe power but not send any trackpoints.

    In the Settings, Messages, Listen Interval

    I can select 2, 5, 10, 20 min, and continuous.

    When I set this to continuous, then the 2 arrows on the display, meaning active communication flash all the time. Battery drain is abt 30% in 4 hrs, unit outside under free sky. With this setting, I can receive a message any time almost immediately.

    Selecting any other (min) disables any reception of messages completely. Let say I take 10min. Under menu item 'Check' the is then an information with title 'Listening for new messages' . Bellow there is time shown when the last *Check* was done, in this case after switch on. Right of it time is shown 'Next listen'. And bellow a down counter is counting to zero and at this time the listen should happen. The counter stops for abt 30sec or so, then next time info 'Next listen' comes up and the down timer starts count again.

    However this goes on and on, there is apparently nothing received and thus no action is taken by the device. This goes on and on and even after a day, no msg is received.

    There is however a green button on lower edge of the screen 'Check now' can be selected and this starts active check, the two arrows flash immediately and qued msg will be received.

    So as far as I could see in last days, I have only following options:

    1. Use the device as tracker, then a check is carried out with every trackpoint anyway

    2. Do not track, but set the listen for 'continuous'. This eats the battery rathe fast, as it is permanetly actively checking for msg.

    3. While not tracking, use the manual check by hand time to time

    The timed option is of no use at all.

    On a Mini, which apparently makes a check each hr (tested, yes after max 1h messages arrives) I have options:

    1. Use the device as tracker, then a check is carried out with every trackpoint anyway

    2. Do not track, but wait max 1h until the msg arives

    3. While not tracking, use the manual check by hand time to time

    As I said, I never considered this to be an issue, but when my users ask, I have to provide an answer. Therefore I am busy with the units for days now, just to figure out what does not work.

    Can it be that:

    the listen, was using the broadcast service (~pagers) and this service does not exist any more?

    As nobody bothered to update the FW of older units, the function is there but not in the sky?

    Do those pagers still work?

    I remember certain .gov orgs tried to buy all the pagers left on the market some years ago, as delivering msg to a device any where in the world without disclosing its position was supposed to be aval for just everyone in the world.

    Mini has no listen function at all, and I was told in 66i it does not exist either.

    I do not know if such function is in the Garmin inreach explorer, the rubber one. Can someone check if this times lsiten is still included there?

  • You're probably going to have to call tech support to get a definitive answer.

    The way you describe the results of the timed "listen" function leads me to believe that this is a passive listen (receiver on and listening, but does not transmit an active query TO the Iridium network). 

    Yes, the passive listens still work. This is why you get the messages in a timely manner in continuous mode. The reason you do NOT get them when listening at 2, 5, 10 or 20 minute intervals is a matter of timing. If the device is not listening at the precise moment the Iridium network decides to send the "ring", the device will miss the message on that attempt. What I would expect is that shorter intervals would produce better results. That is, they would eventually receive the message, but NOT necessarily on the first (or second, or...) try.

    This is why newer devices rely on the active message check rather than the listen functionality. I THINK that the newer devices still do passive listens at intervals. But they no longer provide any user control over the interval. However, I don't know that for a fact and it's impossible to test in any reasonable manner. It doesn't really matter anyhow - the active checks are a superior solution.

    The only downside to the active check is that it can be a bit of power hog in poor conditions. The device is going to try VERY hard to communicate with the Iridium network. In poor conditions, it will retry for a while. This involves both the transmitter and the receiver, and eats a bit of power.

  • OK thanks, I will make some more experiments.

    It is just something wast majority of users tracks and will not notice any problems.