Opticlimate lightcell with Hygrostat PRO2

Opticlimate Light Cell with Hygrostat PRO2

With a PRO2 there are 2 models with a connection of no. 18 0f no connection.

With number 18 you can use the light cell and Hygrostat function 

Without number 18 then you can omit the 18 then you only have Hygrostat function