Sierra Wireless DART 200 CDPD Modem manual Proximity to other antennas

DART 200 CDPD Modem User’s Guide 7 Vehicle Installation Considerations

The application program in the MAS has no way of knowing before attempting a send or receive operation if the modem is still in online mode. The application can be designed to assume that the modem is always online, or to always check that it is online before performing the send or receive operation. In the former case, a send operation failure is indicated by an error return code (in command mode the modem expects to see all messages start with an AT), while a receive failure is indicated by a timeout.

If the MAS can sense the RS-232 interface, as described in CDPD status sensing, p. 8-15, perform this operation to verify that the modem is still connected before attempting a send/receive operation. For Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) the connected state implies that the modem is online. If the MAS cannot sense the interface leads, it tries the send/receive operation first, and only proceeds to error-checking if an error or timeout occurs.

For applications using Serial Line Internet Protocol (SLIP), use the Automatic SLIP restart feature on the modem, to automatically put the modem back into SLIP mode following a power reset.

If the modem is not online, the next step is to check registration state through the RS-232 leads or with ATS57? If it is not registered, the program waits and periodically checks registration status, eventually proceeding when the modem reregisters. It is assumed that the modem is set up to register automatically, as described in Auto-Registration when not registered, p. 8-7.

When the modem becomes registered, the next step depends on whether or not the MAS is a server or a client. If it is a client, the recovery procedure for both TCP and UDP is to issue the appropriate dial command. If it is a server, the recovery procedure for both TCP and UDP is to wait for a call from a client.

Proximity to other antennas

In general, do not locate the DART 200 antenna closer than 5 feet to other antennas (specifically, two-way radio antennas) and in certain cases more separation is required. In many vehicular applications, there are two-way radio transmitters in use and usually the antenna mountings are not 5 feet apart. Interference from the radio transmitter can slow down response times or block modem transmission.

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