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GPRS clocks and signal strength

    When installing a GPRS clock you need to consider what the signal strength and reliability of the signal is at the site you want to install it at.



    Deciding on the clocks location

    Paramount would be to determine the position where the clock will be installed on site and then asses the reception the clock gets at that location. Test the network signal strength using the clock's signal strength meter (details at the end below).  Choose the best clock location based on this reading only.

    Signal strength inside a warehouse made of metal could be non existing, but for example just outside the warehouse, were metal does not shield the network signal you might get a full strength signal. Here a solution would be is to install the clock inside with the antenna outside. Be aware of lighting and the necessary fail safes that have to go with this. Also beware of dead spots at sites.

    Intermittent network coverage is the worst. You would have to determine if this is due to bad network coverage in the area, or if the infrastructure in the area, for example power to the network tower causes no network coverage. The last one you can't do too much about.

    Now that you have the location of the clock and the signal strength at that location, you can determine what type and gain of antenna you require. No need to solve a small problem with a sledge hammer, because over amplifying a signal can cause noise.  Full signal - 5 bars is measures at -59dbm on the clock. If your signal strength is 1 bar (> -109dbm) you need a gain of at least 10dbm to get three bars. A gain of 20dmb to get 4 bars. Generally antenna's giving you a gain of 20 to 30dbm gain are at least 300mm by 300mm in size. The normal antenna we ship with the clock provides a gain of 6-9dbm.

    That said, the antenna we ship is an omni antenna which received signals for anywhere around the antenna. A possible option would be is to install a directional antenna and point it at or the general direction of a network tower or a direction where you believe the strongest signal is coming from. The clock's signal strength meter can guide you with the best direction for the antenna as well.

    Measuring signal strength

    To measure the clock signal strength press 945# on the clock keypad.

    Signal strengths:
    5 bars : >= -59 dbm
    4 bars : >= -89 dbm
    3 bars : >= -97 dbm
    2 bars : >= -103 dbm
    1 bar  : > -109 dbm
    0 bars : <= -109 dbm

    Thus the allowable range is
    Max >= -51 dbm
    Min <= -113 dbm

    Bandwidth specifications

    If you are planning to use another external antenna it is important to understand that not any external antenna will work. Our GPRS module makes use of the following bandwidths:

    Class 4 (+33dBm ±2dB) for EGSM850
    Class 4 (+33dBm ±2dB) for EGSM900
    Class 1 (+30dBm ±2dB) for GSM1800
    Class 1 (+30dBm ±2dB) for GSM1900
    Class E2 (+27dBm ± 3dB) for GSM 850 8-PSK
    Class E2 (+27dBm ± 3dB) for GSM 900 8-PSK
    Class E2 (+26dBm +3 /-4dB) for GSM 1800 8-PSK
    Class E2 (+26dBm +3 /-4dB) for GSM 1900 8-PSK

    An external antenna made for Wi-Fi will not work as it's frequency is around 2.4Mhz even though it also has an SMA connector. 


    APN Settings on SIM cards

    Please ensure the APN on the SIM card is indeed configured by your service provider as "Unrestricted". In order to have this done one has to follow the correct procedures. 

    • Download the required form from the link below.
    • Complet it with the necessary information.
    • Submit to the service provider.
    • Follow up with the service provider in a few days on whetehr it has been done.
    • Test the clock to see if it is indeed acessable.


    Currently only Vodacom SIM cards are supproted with our clocks.

    If the APN is not cofigure to "Unrestricted" you will experience communication problem in that you cannot access the onboard clock web interface as well as where CSTime (Time & Attendance software) can not interact with the clock effectively.



    Download the "Unrestricted APN" document below. Proceed to complet the form & send it through. On the form where it says reason for access write down "Point to point communications".


    Step 1 – Fill in the APN document and have a copy of the applicants ID Book

    Step 2  - Email the APN document along with the ID Copy to vodacomshop.tygervalleycustomercare@vodadealers.co.za  . The

    Email subject should read “Unrestricted APN” . 


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    Page last modified 12:32, 16 Jan 2017 by Duaine CS TimeClock Documents > Hardware > GPRS clocks and signal strength


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