Idea behind BACnet Protocol

Digital system came from numeric, in 1980’s we have predominantly numeric controls, but still, in nowadays, peoples are working with numeric controls. Numeric controls are the first interoperable system (Interoperability is a property of a product or system, whose interfaces are completely understood, to work with other products or systems, present or future, without any restricted access or implementation.) The best example of an interoperable system in which one can install its plant with different vendor’s instruments. One could use a thermostat from one company and actuator from another company and can make the system work.

So numeric controls are the pyramid of interoperable and interchangeable systems, which can be easily compatible with other systems.

The advantage of the interoperable numeric system is that, if we have a device from brand A, then, later on, we can replace it with brand B in the network, and will not affect the operation. But back in 1980’s, we had started working with direct digital controllers (controllers having some microcontroller and input, output devices, for example, Some system measures the temperature and control the valve directly), which has not interoperable because everybody built their own controller. It means brand A is not compatible with brand B at any level.

So the problem is if someone wants to increase its facility so he has tied with the original manufacturer because there is no interoperability. Then people start working with the open protocol (An open protocol allows vendors' equipment to interoperate without the need for a proprietary interface or gateway. They talk the same language and no translation is needed).

So the people from ASHRAE, there were thinking about the ways to make digital controls back again numeric control which has the functions of interchangeability and interoperability to bring the overall system cost down. Today most widely used open protocols are BACnet and LON.