Closed protocol is a dedicated protocol designed for a single range of panels examples of this are menvier, gent, notifier, ADT. Basically with a closed protocol system you have to use these devices and any works or alterations to system require dedicated software and or engineering codes. Most likely accompanied by a visit from the company's engineer or a Dedicated Systems integrator. Open protocol are Morley IAS, Kentec, Advanced and others they still require the same devices used throughout the system but are much more widely available so allowing any engineer to replace devices . Complete type changes etc. Most require the use of a laptop but the software is widely available for a one off charge.
Advantage of closed protocol the engineers receive much more detailed training on their systems in house and can quickly diagnose faults . Disadvantage most alterations/additions require a visit from there dedicated engineer at a premium