Presevi offers master slave controller for interconnecting several air conditioning units to a single master controller as a building management system. This unique feature of the controllers result in considerable energy saving, low operational cost and short pay back period. The master slave controllers can monitor and control conditioned area from remote locations situated anywhere using password/ modem/ pstn/ internet, etc. The system consists of a master controller and several slave controllers that can be connected to internet. The company provides these controllers with in-house windows-based management software and picmas 4.0 for operation. The master controller comes with advantage of being connected to pc either at the site or at remote location using pstn and modem. The master controller with a powerful micro controller is provided with both rs485 and rs232 ports. The slave controllers are provided with a separate micro controller and operate the air conditioner units as per set control parameters and interlocks that can be connected to the master controller using rs 485 port. A pc/ modem could be connected to its rs 232 port.