The DialOut/EZ solution for using a dial-out modem server instead of dedicated modems

To collect data from utility meters that have a modem interface, AMR applications need to make modem calls. The conventional approach is to add modem hardware to each computer that runs the AMR software.

The Problem

Unfortunately, this means that each copy of the AMR software is tightly coupled to a computer at a fixed location with a limited number of dedicated modems.

The DialOut/EZ Solution

Instead of using dedicated local modems in its application server, each AMR application uses a pool of shared dial-out modems provided by one or more modem servers.

The DialOut/EZ Redirector is installed on each AMR application server. The redirector is configured to provide virtual COM ports corresponding to the maximum number of modems that the AMR application will need to use at one time.

The AMR software is not modified, but simply reconfigured to use DialOut/EZ virtual COM ports instead of local COM ports. (Alternatively, the AMR software can use Windows modem devices.)

Each time an AMR application opens a virtual COM port, the DialOut/EZ Redirector immediately obtains the next available modem from one of the servers in the dial-out modem pool.

To the AMR application, the modem appears to be directly connected to a local COM port. The AMR application retains sole control of the modem until it closes the virtual COM port, after which the modem is returned to the pool of available modems.

Advantages of the DialOut/EZ Solution

• The AMR application can be run on cost-effective application servers that can be located anywhere on the network.
• Multiple copies of the AMR application can share centralized modems, often digital modems on T1/E1 lines, that are easier to administer and maintain.
• Multiple modem servers can be used as a global modem pool so that each modem server is not a single point of failure.

Modem server selection

Modem servers from Cisco and Multi-Tech are two examples of off-the-shelf equipment known to work well in many AMR applications.

In some applications, more reliable modem connections are achieved using a PC-based modem server with multi-modem boards and Tactical's TacServe COM Port Server software. Modem products from Eicon, Comtrol or Multi-Tech may be able to negotiate better connections with the modems on older meters.

Using multiple modem servers

The DialOut/EZ Redirector has an automatic failover feature that supports the use of more than one modem server. If the primary server is full or unresponsive, DialOut/EZ automatically can move on to use alternates. In this approach, the total modem capacity is divided among two or more modem servers.