There are three basic modes in which a group of PCs and/or terminal servers can communicate with each other

 

• Many-to-One

• One-to-Many

• Many-to-Many

 

All of these distinct modes have advantages and disadvantages, however whichever one you need to use, the Redirector will support it.

 

Many-to-One is most often used when a number of things each want to send a message to the central controller. There is no polling from the centre, just messages sent from each device. The central hub may or may not respond to these individual messages.

 

One-to-Many is the opposite - a central hub polls outlying devices, and they respond. Many SCADA systems work this way, the central controller demands a status report from each outlying data acquisition box, concentrator or RTU. The outlying box responds only as a result of its poll.

 

Using the Redirector, existing RS485 networks can be replaced or augmented, see Replacing RS485 networks

 

A variation of the One-to-Many theme is broadcast, whereby the central device sends out messages that are heard by all the outlying devices, but there is never a response. This is usually an information display application. Examples would include signs in an airport or railway terminus, or information display boards in trading rooms. Note that not all the signs need to be showing the same information; the signs may be addressable, which implies the serial data is packetized and has an addressing scheme. An example of this may be roadside bus information displays, each of which needs to show different information, but all signs can be on a common communication network.

 

A Many-to-Many configuration is described in Replacing RS485 networks

Usage Examples

Usage Examples