The 5820XL supports either the SK (System Sensor) or SD (Hochiki) protocol, but these protocols cannot be mixed on the same system (Page 1) [1].
Device capacity per loop depends on the protocol used:
SK Protocol: Each loop supports up to 99 detectors and 99 modules, for a total of 198 points per loop (Page 13) [1].
SD Protocol: Each loop supports up to 127 devices in any combination of detectors and modules (Page 73) [1].
The system includes one built-in signaling line circuit (SLC) and can be expanded with up to three 5815XL SLC expanders for a total of four loops (Page 13) [1].
