I have a RKL 3 with 8 plugs (2- PC4s) and 1 SL1. The SL1 has 2 bus connectors and 2 BNC connnectors. I use 1 bus connector to connect the SL1 to a PC4 and the other to connect the temperature probe (itemp), and I use one of the BNC connectors to connect the pH Probe. There are 3 additional connectors for additional probes.
The SL2 is not compatible with the RK lite at this time as far as I know, it is for the RK Elite.
I am very happy with the RKLite, I have it controlling my lites with timers setting on and off times and the MHs will turn off if temp gets too hot. Also have my skimmper and return pumps hooked up to it so I can turn them off for 15 minutes while feeeding or doing a water change. Having it controlling my heater as well. It is very easy to use tho the instruction manual sucks. You will have to go to their website and check the support forums for many answers to the easiest questions/situations not covered in the manual.
I LOVE IT! LOL works great once you get it all set up. It is very easy to use , I just wish they would have spent more time and thought on the instruction manual.
