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Frequently Asked Questions
The DLM4000 Dial-up/Leased Line Modem
Q: Can I use the modem in my PC/Laptop to communicate with a Data-Linc DLM4000 in the field?
A: The DLM4000 comes pre-configured from the factory to communicate effectively with PLC's. To do this, it is necessary to set some of the registers in the modem in ways that differ from register settings that may be found in other modems. Because of this, connectivity with other modems may not be possible without changing the registers in the other modems. In some cases, it's not possible. Because different modems have different register settings, it is difficult to determine ahead of time if a given modem will interface with the DLM4000. It is also worth noting that changing the register settings in the DLM4000 would inhibit its ability to communicate with a given PLC. The only way to assure reliable communications when using the DLM4000 is to have one at both ends of the connection. In the long run, it is the most cost-effective way to go. In any case, it is always best to contact one of the Data-Linc applications engineers to discuss your specific installation.
Q: If I have a multi-drop communication circuit provided by the local phone company, can I use a DLM4000 Leased Line modem as part of a multi-point system?
A: Because the DLM4000s uses handshaking when communicating with each other, it is not possible to have a multi-point system when using DLM4000s. A possible solution (depending upon the specific application) might be the LLM1100.
Q: What happens if the phone connection is dropped?
A: An Auto Alarm Dial Back module is available on the DLM4000. This gives the remote PLC the ability to establish a data path to a Master PLC or PC via a logic input from the remote PLC to the Auto Alarm Dial Back module. This could be used for remote alarming or time based data updates.
Q: Why should I buy a DLM4000 when a standard lower cost off-the-shelf modem could work?
A: The DLM4000 Dial-up/Lease line modem is specifically designed for industrial data acquisition and control applications. Command, control and data collection protocols require a more robust and reliable level of communications. Where high-speed data compression and multi-level error correction may be desirable for Internet connection or faxing, in most cases it will inhibit PLC communications. Another area to look at is Data-Linc's knowledge of the Industrial Automation industry. Data-Linc Group is a third party partner with the industries major PLC manufactures (Allen-Bradley, GE Fanuc, Modicon, etc.). Because of these alliances, Data-Linc has become a leader in PLC communications "know how. " This is reflected in the design and configuration of our modems and in our ability to technically support them and the applications in which they are used. In the long run, when a customer purchases a Data-Linc DLM4000 (as well as any of our other modems), they are given a high level of confidence that from installation to long term operation, they will have trouble-free connectivity and communication.
Q: How tolerant of temperature extremes are these modems?
A: The DLM4000 will operate reliably at temperature ranges of 0° to 60°C (32° to +140°F).
Q: What is the difference between Data-Linc's AE485 and AE422and RS485/422?
A: Data-Linc uses "AE485/422 2-wire/4-wire" that is compatible with RS485/422 2-wire/4wire. AE, which stands for Auto Enable, is a Data-Linc proprietary technology that is compatible with RS485/422. The default for RS485/422 is receive mode. The AE function allows the device to transmit when data is fed to it without the need for a separate enable signal. Auto Enable is particularly important and beneficial in multi-dropped two-wire 485 and some four-wire 422 solutions. When interfacing with our products, wire count is most important. Please check with non- Data-Linc product manufacturers for their specifications. For further clarification contact Data-Linc at (425) 882-2206 or email techsupport@data-linc.com.
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