Application for all W&T devices with Ethernet connection:
Wireless LAN
There are many situations in which it is not possible or would be very expensive to connect devices to an existing network by cable:
- "Islands", that are far from the cable infrastructure, e.g. in large production halls or warehouses or in a separate building.
- Devices used in a very mobile and flexible manner, whose location within a hall or premises frequently changes
- Movable mounted parts of production systems that otherwise could only be connected with expensive trailing cables.
W&T components in the wireless LAN
When the object is to communicate with serial devices, monitor digital states or check temperatures, one is increasingly confronted with the need to integrate W&T components in wireless LAN environments. Due to the still unstable standardization situation, these cases lend themselves to the combination of a 10/100BaseT standard device with an external wireless conversion in the form of a wireless Ethernet bridge or a suitable wireless access point. Switching later to another wireless infrastructure then just involves exchanging this bridge. The often sensitive, actual application, consisting of Com-Server or Web-IO and the controlling software, remains totally unaffected by this change of infrastructure. The following examples for Com-Server, Web-IO Digital, Web-Thermo-Hygrograph clarify the basic structure.
Illustration 1 shows, with the aid of the W&T Com-Server, a serial device, such as a machine controller is driven over the company network. With the help of the "COM Port Redirector" a virtual "serial port" on the PC is accessed and redirected to the device over the company network as well as the Com-Server.
Illustration 2 shows a W&T Web-IO Digital used to read digital inputs and trigger digital outputs over an RF network. In addition, when there is a state change in certain inputs an e-mail is sent to any desired previously defined address.
Illustration 3 shows monitoring of temperature and relative humidity using the W&T Web-Thermo-Hygrograph over a wireless LAN. Here again a browser interface as well as an e-mail alarm function is available.
Fig. 4 shows a W&T RFID Server which is detecting arriving and leaving tags and writing them to a database using a wireless LAN.
Wireless LAN components
The central component of a WLAN cell is the access point. Comparable with a hub or switch in "wired" networks, this access point works like a star coupler for the WLAN stations in its range. In addition, it often needs to act as a link between the wireless cell and the cable-connected network. On the terminal device side, such as PCs or notebooks, the wireless connection to the access point is made using so-called client adapters.These are generally implemented as a PC card or USB device.
Terminal devices which are fitted only with a traditional Ethernet terminal and do not have a USB port or PC card interface are incorporated into the WLAN using wireless Ethernet bridges. This works something like a media converter between wireless and 10/100BaseT. Pricewise such wireless client bridges are currently less than the access points from the same manufacturer.
You are encouraged to procure the components for the wireless LAN from the same manufacturer, since in spite of all the assurances there is not always interoperability between products from different manufacturers. This applies in particular to the various capabilities and characteristics with respect to encoding. Nor can the user, given the current rapid continued development, use this method to build a "core" of WLAN components which can be easily exchanged when technology changes.
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