\Over here you can see the current status of all your Intelligent Active GPRS Modems.These are all the modem types that connect to Plug and Play Scada over GPRS and where the connection is maintained.\
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This include modems that can give us the SIM card number while connected over TCP/IP: \
TruTeq modems, some KoCoS modems and Siemens TC65 modems. It excludes modems which can't do that, for example Landis & Gyr modems, Maestro modems and Enfora modems.Active GPRS Modems that are not intelligent would be set up to connect to a unique port. The Server port is only created when the meter is read.\
In contrast, intelligent GPRS Modems are connected all the time. Each modem type connects to the same port, since Plug and Play Scada can interrogate each connection so as to know their SIM card number.The benefits of using an intelligent Active GPRS modem as opposed to an unintelligent Active GPRS modem are:\
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- Faster performance: When a meter is read, it can establish a 'connection' to read it very quickly, since the modem is probably already connected.\
- More Reliable performance: Plug and Play Scada will attempt to read an out of date meter as soon as the modem connects, meaning that even if the modem only has GPRS connectivity for 5 minutes per day, Plug and Play Scada will use that time to read the meter, instead of waiting for the normal scheduled time to make the read attempt.If you navigate to the link with the SIM card number, you can see a report of when the particular modem connected or disconnected from Plug and Play Scada. This will give you a good idea of the reliability of GPRS at a particular site.Each connection is kept alive with a watchdog packet in less than a minute, meaning that the connection remains bi-directional even when it is from behind a fire-wall, and that the modem and the server will both know when the GPRS connection fails.\
The watchdog are in some cases uni-directional for 10 to 20 minutes before it does a bi-directional watchdog. This is to cut down on the traffic to save money, since a bi-directional watchdog costs twice what a uni-directional watchdog costs. That also means that it will sometimes take up to between 10 to 20 minutes before the server notices a connection from the modem has dropped, since the network inbetween does not necessarily register a broken connection.\
The cost of the continuous watchdog is generally less than R7 per month in South African conditions at the time of writing (June 2010). | \