Stargate shields needs energy to operate and can be controlled directly by the DHD if installed. Need energy to operate all the time but can work with naquadah from the DHD. A stargate without DHD cannot handle a shield because the lack of the appropriate control crystal. The shield can take its energy from RF or EU if there is no energy inside the stargate. The shield blocks all communication from the gate, excepts sendMessage() and GDO messages (from my other suggestion). A stargate can has an iris and a shield in the same time. The shield also protect entities from the vortex splash. The shield can be controlled from the API as well as the iris. GDO open both iris and shield when used.
Stargate shields needs energy to operate and can be controlled directly by the DHD if installed. Need energy to operate all the time but can work with naquadah from the DHD. A stargate without DHD cannot handle a shield because the lack of the appropriate control crystal. The shield can take its energy from RF or EU if there is no energy inside the stargate. The shield blocks all communication from the gate, excepts sendMessage() and GDO messages (from my other suggestion). A stargate can has an iris and a shield in the same time. The shield also protect entities from the vortex splash. The shield can be controlled from the API as well as the iris. GDO open both iris and shield when used.