User Manual

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Cellular Networks
3.4 How to Connect Serial Devices to Cellular Networks
Traditional Modems
Serial port connections are very popular in traditional industrial applications but their transmission distance
is limited. The Hayes command modem (AT command) offers a good solution for enlarging the transmission
distance. It connects two serial devices through PSTN via an AT modem. This traditional modem always
occupies the line as a voice call so even when you are not talking (transmitting data), you will still be charged
by the minute for staying on the line.
In addition, the serial device (such as a PLC) link to the modem needs dial-up capability for call controls, such
as dialing a number, checking if the called side is busy, retrying the call, and hanging up. If the connected link
is an IP domain, then the serial device needs built-in PPP (Point to Point Protocol) capability to access the IP
domain, whether it is an Internet or VPN. Serial devices also require many call control capabilities in order to
link to traditional modems, resulting in heavy loading.
IP modems, equipped with call setup and PPP capability to reach IP Internet domains, offer a viable solution
that reduces loading for serial devices so they can focus on transmitting and receiving serial data. Cellular
networks are everywhere so you can make calls without a wired telephone connection, providing industrial
automation machine-to-machine applications with additional benefits.
IP Gateways
IP gateways are not only call setup intelligent but also come with built-in TCP/IP capability. Due to the
popularity of cellular networks around the world, you will be able to use them to communicate from just about
anywhere. Moreover, IP gateways can help your serial devices transfer and receive data conveniently.
Moxa‘s cellular IP gateways solution offers flexible communication for serial devices.
Keep Existing Software (Real COM / Reverse Real COM)
Moxa’s Real COM and Reverse Real COM operation modes are used to link remote serial devices to the
control center. By simply installing OnCell Driver Manager onto a host computer at the control center, your
applications will be able to keep existing serial interface software to transfer and receive data from the serial
devices.
Here’s how it works:
• Installing OnCell Driver Manager onto the host PC allows the host PC to connect directly to remote serial
device.
• The serial device is connected to the OnCell G3100’s serial port.
• The connection is maintained automatically between OnCell Driver Manager and the OnCell G3100 device
to access the serial device over a cellular network.
How OnCell Cellular IP gateways can help your serial device
access an IP domain:
• Keep existing software (Real COM / Reverse Real COM)
• Standard TCP IP connection (TCP server / Client)
• Real-time serial data send/receive solution
• Short message connection (SMS Tunnel)
Network capabilities for data bearer:
• IP gateways over CSD
• IP gateways over GPRS