Why is an

Quote:

Ordinary wireless device is prohibited to use.

as this is the typical method used for a measly 1.5km link.

There is also a method called 'free space transmission' which is using a laser to pass the information. It can be invisible.

The most common is a simple radio link as it is also the most reliable. It would be more reliable than Internet Service.

If the stations are connected by pipe that's insulated from the ground that could possibly be put to use.

Keith Cress
kcress - http://www.flaminsystems.com

If you get mobile telephone coverage then I'd assume that it'd be possible to use that for some sort of broadband communication between the sites, as opposed to what I am assuming is fixed line internet install.

However, the reliability requirements of the link have not been stated. What is the penalty if the link goes down? Is any signal failure already handled in the equipment, or does some sort of connection link monitoring need to be considered?

Radio links would also be an option.

EDMS Australia

Have you considered using Ethernet comms (fiber-optic link)?

What do you mean by "ordinary wireless device"?
There are industrial IO wireless links that will do what you are looking for, operating in the 902-928 unlicensed band that are not consumer grade wireless.
You could install one radio at each end with yagi antennas.

Cellular modem
Laser or microwave comm

TTFN (ta ta for now)
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A pair of wired-in/wired-out 1 watt 900 MHz ISM radios from Banner Engineering (DX-80 “premapped” kit) or Phoenix Contact RadioLine. Like Robertjo says, yagi on each end and some elevation on a pole or bldg roof to get over the trees.

A DI on one end is a DO on the other end.