Before there were PCs and Local Area Networks, there were main-frame computers and terminals. Many companies and institutions still use this type of system although the main-frame host computer is now usually a newer, more powerful, and less expensive mini-computer such as the IBM RS/6000 or HP 9000 series.

These systems use terminals connected by cables to the host computer. Nothing difficult about that until you want to link two or more buildings together. Fortunately there is equipment available to consolidate the data of multiple terminals to pass it across either a telephone line or a wireless link.

Sometimes we only need to have a single user positioned away from the main group. As an example, a car rental company needed to have a single terminal positioned out in the parking area for the employee checking rental cars in and out. This was done with a wireless modem.

Sometimes you need to have a whole group of employees connected at a remote location as in the case of a branch office.

In these situations, we can use a multiplexer to combine data from the remote terminals to a single data channel that can then be sent across a telephone line. If the buildings are close enough, we can eliminate the recurring cost of the telephone line by using a wireless system. Once the data channel is received at the site with the host computer, another multiplexer separates the data back out to the correct individual ports on the host system. In this way remote users have the same access to the system as local users do.

Companies using a PC network can also link between buildings. Again, if the distance is not to great, we can do this using wireless equipment to avoid the cost of a telephone line.

Here we use routers or bridges to link the network connections using a telephone line or use a wireless bridge to make the link. Users at either location can access files, send email, or print as if they were all in the same building.

There are occassions when because of the type of business or special requirements of the building, it may be to your advantage to consider a wireless Local Area Network.

Here we can have a complete Local Area Network without running any wires in the building between individual computers. This has proved handy in several situations:

• warehouse operations and hospitals where workers are mobile

• for historic buildings where holes drilled in walls or floors would detract from the appearance or value

• old buildings where asbestos abatement would cost many times the value of the wireless network equipment

• large open buildings where there are not good places to run network cables

• office buildings where employees are in hard to wire cubicles or where the office configuration is subject to change