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Thread: GSM Dialers

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    Senior Member IPAlarms's Avatar
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    Default GSM Dialers

    Before the crash, I had some great private messages on the subject of using a GSM dialer between a control panel and an alarm receiver and I remember there was a wealth of information in other posts on this subject. I've tried a search in the Security Alarms forum for GSM but nothing comes up. I'm assuming it's all been lost, so forgive me for going over stuff that might be a bit boring for some of you - it's all new to me.

    Basically, I am doing some research on the pitfalls of installation and setup of GSM dialers and also any problems with failures to communicate - and why this happens. I don't care about different makes and models - just want to start a general discussion on the subject.

    Anyone like to start this off by telling us about their experiences with GSM dialers ?
    Developer of VoIP2Go at ozvoip.net - Alarm compatible VoIP Network



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    Number 1 rule when dealing with ANY GSM product. It WILL lock up. How the various manufacturers detect and deal with these lockups is very important to product stability.

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    Quote Originally Posted by madtech View Post
    Number 1 rule when dealing with ANY GSM product. It WILL lock up. How the various manufacturers detect and deal with these lockups is very important to product stability.
    Thanks for the info.

    How do the more professional manufacturers deal with this problem?

    My guess is that they would have to somehow power cycle the unit, but I can't figure how this could be automated unless it has a self test feature.
    Developer of VoIP2Go at ozvoip.net - Alarm compatible VoIP Network

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    Sir, have you previously any experience with a "watchdog", many systems (dvrs', pcs' etc etc) have this feature implemented for this reason, Fault recognised, system is cycled and system returns to normal.

    How would you go with a "dual sim" gsm...???

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    So what your saying is that any system that has a "watchdog" feature implemented will not lock up or "stop" functioning as normal?

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    So, when a unit "locks up", is there always a loss of dial tone ?
    Developer of VoIP2Go at ozvoip.net - Alarm compatible VoIP Network

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    NO, Incorrect by good friend (Mr storm)
    A watchdog feature, simply checks for the fault and then restarts the process to correct it

    YOU haven't ever looked inside a dvr (pc based), on a decent capture card it will have two pins, the "reset" is moved to here and then jumpered back to the case button. This only helps in the process of faults.

    How many systems can I think of with such a feature, well now.


    I have to appolgise for my grammar, but this is my understanding of the topic at hand,
    Most embedded systems need to be self-reliant. It's not usually possible to wait for someone to reboot them if the software hangs. Some embedded designs, such as space probes, are simply not accessible to human operators. If their software ever hangs, such systems are permanently disabled. In other cases, the speed with which a human operator might reset the system would be too slow to meet the uptime requirements of the product.

    A watchdog timer is a piece of hardware that can be used to automatically detect software anomalies and reset the processor if any occur. Generally speaking, a watchdog timer is based on a counter that counts down from some initial value to zero. The embedded software selects the counter's initial value and periodically restarts it. If the counter ever reaches zero before the software restarts it, the software is presumed to be malfunctioning and the processor's reset signal is asserted. The processor (and the embedded software it's running) will be restarted as if a human operator had cycled the power.

    --------------------------------------------------------------------------
    For my learnered friends not in the know, I went to my trusty Wikipedia source (well known for lots of factful knowledge);
    Computer hardware timing device that triggers a system reset if the main program, due to some fault condition, such as a hang, neglects to regularly service the watchdog (writing a “service pulse” to it, also referred to as “petting the dog” or "kicking the watchdog"). The intention is to bring the system back from the hung state into normal operation. - more here
    (heres my source, so you do not make the demeaning attempt at picking on my point of view)

    @ Mr Ipalarms, In my experience I have found that yes it does take the line (guardcell GSM), I can even have my Telstra friends verify this as they to have been called out to check the faults on the PSTN, without issue it has been the GSM, rebooted and alls perfect (till the next time)

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    OH good sirs, I forgot the humble Pc based dvr- with the "daily" reboot, as a function you would find close to hand, as discussing space craft maybe out of your league, I'm sorry my good friends, to belittle you in that manner, it was not my sole intention.

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    Well I guess the watchdog function built into the range of systems that we use have issues of reliability seeing as a number of us have verified that they indeed lockup & on occasion hang without rectifying.

    As for space craft.....yes out of my league, but im not surprised that its not out of yours.

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    ....and meanwhile back on planet Earth....

    Is a daily power reset acceptable for such a device ?

    Regarding dial tone - I meant the dial tone provided by the GSM network - not PSTN. Let's assume that there is no PSTN line available, the GSM device locks and a panel attempts to go off hook - will it hear a GSM network dial tone ?
    Developer of VoIP2Go at ozvoip.net - Alarm compatible VoIP Network

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    Quote Originally Posted by IPAlarms View Post
    Is a daily power reset acceptable for such a device ?
    ?
    Ip alarms, Which the DVR or the GSM,

    For one, the DVR- yes, why not, it takes approximately one minute for a cycle, depending on the specs of the pc, but it would not be preferred to have to rely on this function in case theres a robbery, or such issue at this specific time of "cycling". Depends on the installation and the customers requirements, if its high security, you would use a more High end machine in my mind.

    GSM, well I don't think so, what happens if this is HARD coded for every unit and someone had this information, you could simply commit the crime during the "cycling" time,
    I think its poor design (lack of R+D) on the manufacturers part. But we have to live with what we have at hand. There again, one cant sell what the customer needs, but more of what we have to sell them - this is dictated by the suppliers of the world.

    As for space, I'm sorry for even commenting. I just offered a serious explanation and your now sledging me once again. With every remark I make, are you going to continue to "sledge" me, because thats what it seems like to me.

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    The best way to set up a GSM is to ensure the unit that is purchased is "intelligent" such as the SED62, you are able to programme a CMS's reciever numbers into the unit, and of course an account number, by doing this you can set the unit to send a test signal every 24 hours, weekly if u have to !

    The thing to check first is that your CMS is able to monitor the GSM that you are installing, and are able to recieve 2x test trasnmissions on one account number, (dialler & GSM) if they are not able to (such as sims, unless a re-direct toa sub account is used) you need to request a new account number for the GSM.

    The SED unit's are able to recieve SMS requests, some times these units do lock up for various reasons, so you simply send a command via sms and the unit will reboot, after this u send another request for a test signal to the CMS. (all this is done remotley) in my opinion the SED62 is one of the best GSM units currently on the market, i just get the shits when they arent installed correctly... how many do u guys come across that dont use the "GSM FAIL" contacts to the main panel.. DODGE!!

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    OK - Thanks guys.

    It sounds like we have the option of making the device power cycle on a daily basis, or having the CMS monitor daily test signals. If they do not arrive - power cycle remotely via SMS.

    Now let's assume we have a second "intelligent" device available on site that can constantly check if the GSM device is alive. My first thoughts would be to check for GSM dial tone and if it is not available - reset.

    Are there any other ways to detect if a unit has locked ?

    keef82 mentioned the GSM FAIL contacts on the SED62 - which sound ideal. I'm just wondering how the SED can control this relay if it is locked ?
    Developer of VoIP2Go at ozvoip.net - Alarm compatible VoIP Network

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    Quote Originally Posted by IPAlarms View Post
    OK - Thanks guys.
    It sounds like we have the option of making the device power cycle on a daily basis, or having the CMS monitor daily test signals. If they do not arrive - power cycle remotely via SMS.
    I don't think so, I have to many in the field and this is not cost effective, not from the sms cost, but the time taken to manage these systems.

    Quote Originally Posted by IPAlarms View Post
    Now let's assume we have a second "intelligent" device available on site that can constantly check if the GSM device is alive. My first thoughts would be to check for GSM dial tone and if it is not available - reset.
    Maybe on a medium / Large sized system, with enough outputs etc to enable you to wire a configuration to effectively do so. [/quote]

    Quote Originally Posted by IPAlarms View Post
    Are there any other ways to detect if a unit has locked ?
    One must wonder. - if the GSM fail on the device is wired into an input on the panel and an output is wired into the GSM to reboot.

    Quote Originally Posted by IPAlarms View Post
    keef82 mentioned the GSM FAIL contacts on the SED62 - which sound ideal. I'm just wondering how the SED can control this relay if it is locked ?
    They all have them, like Keef82 mentioned how many wire them in?


    DODGY
    Last edited by AusSecTec; 28-01-08 at 03:33 PM. Reason: Add content

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    I know of at least one system that if it looses network registration for x time it does a reboot

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