Systematic Capability is achieved when the equipment used to implement any safety function is designed using procedures intended to prevent systematic design errors.  The rigor of the required procedure is a function of a Safety Integrity Level (SIL). This is evaluated through an assessment of the quality management system for suppliers of process control and instrumentation for safety against the requirements in IEC 61508.  If the QMS meets the requirements of 61508 a SIL Capability rating is issued.  The rating achieved depends on the effectiveness of your QMS.  The IEC 61508 certificate indicates the systematic capability of a product.  

SIL based on Systematic Capability e.g. SC3 (SIL 3 Capable)

The equipment used to implement any safety function must be designed using procedures intended to prevent systematic design errors.  The rigor of the required procedure is a function of SIL rating.  

Each SIL rating (Levels 1-4) has different requirements to be met if a product is to achieve that SIL rating. For example, SIL 1 Systematic Capability rating, or SC 1, will have X number of requirements to be met, while a product that has a SIL 2 Systematic Capability rating, or SC 2, has to still meet all of the SIL 1 requirements (X), while also meeting the additional SIL 2 requirements. 

Fun facts:

• The systematic capability of a product is one of the 3 design barriers that must be met for certification. (Link to blog about 3 barriers and cert)
• Is a limiting factor in SIL. So if your systematic capability meets a SIL 2, it can only go into a SIL 2 SIFor lower (SIL 1 or no SIL). It cannot be a part of SIL 3 SIF.
• Systematic Capability shows your defense against systematic failures or errors due to quality, or design or processes and procedures.

If you wish to see if a product is certified, and find its systematic capability, you can search on the SAEL.