Dedicated modems for compact PLCs and micro controllers

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Mitsubishi Electric is introducing a line of intelligent industrial modems for its Melsec FX compact PLCs and Alpha XL micro controllers. Known as the Mitsubishi Alarm Modems (MAM), these have a non-volatile memory and internal processors for handling the entire data communications process; they are configured via an easy-to-use alarm editor software tool called MX Alarm Modem Editor. This places no addtional load on the controllers, which might otherwise impact on the data communications process, memory capacity and cycle times.

The modems provide access to remote machines, automated systems and plants, enabling inexpensive implementation of remote maintenance, diagnostics, monitoring, alarms and teleservice applications. They operate over international analogue telephone networks or the European-standard GSM digital mobile networks in the 900 and 1800MHz bands. Standard modems are also available for simple telemetry applications.

Mitsubishi modems are autonomous communications controllers with their own 32-bit microprocessors and up to 66 megabytes of Flash memory. They can send data by SMS text messaging, email or fax and can receive by SMS. They are preconfigured with controller protocols so do not require a driver to be loaded in the controller nor changes to be made to the controller program.

They mount on DIN rail and connect to their associated controller with a standard serial cable. Alarm messages, telephone numbers, email addresses and other data are entered with the MX Alarm Editor software. Up to 100 addresses, message texts, controller values and alarms can be stored in the modem. With a few mouse clicks the user can link message texts (the length of which is not limited) to controller values (current operating data, inputs and outputs) and target addresses to alarms.

A multi-level alarm plan, referred to as the 'alarm cascade', makes sure that important messages reach the addressee promptly. If a message is not confirmed within a preset period the modem automatically sends messages to other addresses - if necessary, using different communications channels. This ensures that service staff responds quickly to malfunction information and maintenance requests.

The modem also provides access to the entire controller program for remote maintenance functions. Users in any location can quickly obtain an overview of the current production, machine or plant status. Caller number identification prevents unauthorised dial-ins and additional security is provided by support for connections with a user name and password system. The modem can also be configured to send a confirmation to the user when a command has been executed.

Modems with remote maintenance and teleservice functions are particularly useful for distributed applications with small devices and stations that are not connected via a control network. Using modems, controllers in remote locations and mobile systems can be inexpensively integrated into modern service concepts. Typical applications include: building services; heating, ventilation and air conditioning (HVAC) systems; tank storage facilities; pump and water stations; and container transporters and other specialised vehicles.

04 September 2006

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