PLC and addressable serial communication

I work on elevators and I was wondering if any of the PLC manufacturers have addressable contacts that could be used for tying multiple floors of hall buttons in parallel using only 4 wires as an example.

Most larger PLCs allow for the connection of some form of field bus. Examples of field buses would be AS-i, CanOpen, DeviceNet. For a simple application like this (only digitals) I would use AS-i it only needs 2 cores (unshielded) and required power is also available on those cores

I agree with GeoffC on the ASi alternative. A lot of companies offer ASi products. Here is the link to the site
http://www.as-interface.net/Membership/Members/

Edit: Cant get the link working properly, but click on the member tab to the left.

Kalle

Thank you both for the replys