diff --git a/presentations/fmea/fmea_pres.tex b/presentations/fmea/fmea_pres.tex
index 767447d..de28066 100644
--- a/presentations/fmea/fmea_pres.tex
+++ b/presentations/fmea/fmea_pres.tex
@@ -333,8 +333,63 @@ FMEDA is the methodology behind statistical (safety integrity level)
 type standards (EN61508/IOC5108).
 It provides a statistical overall level of safety
 and allows diagnostic mitigation for self checking etc.
+It provides guidelines for the design and architecture
+of computer/software systems for the four levels of 
+safety Integrity.
+For Hardware 
+
+FMEDA does force the user to consider all components in a system
+by requiring that a MTTF value is assigned.
+This MTTF may be statistically mitigated (improved)
+if it can be shown that selfchecking will detect failure modes.
 \end{frame}
 
+\begin{frame}
+Failure modes are classified as Safe or Dangerous according 
+to the putative system level failure they will cause.
+The Failure modes are also classified as Detected or
+Undetected.
+This gives us four level failure mode classifications:
+Safe-Detected (SD), Safe-Undetected (SU), Dangerous-Detected (DD) or Dangerous-Undetected (DU),
+and the probablistic failure rate of each classification 
+is represented by lambda variables
+(i.e. $\lambda_{SD}$, $\lambda_{SU}$, $\lambda_{DD}$, $\lambda_{DU}$).
+\end{frame}
+\begin{frame}
+\textbf{Diagnostic Coverage.}
+The diagnostic coverage is simply the ratio
+of the dangerous detected probabilities
+against the probability of all dangerous failures,
+and is normally expressed as a percentage. $\Sigma\lambda_{DD}$ represents
+the percentage of dangerous detected base component failure modes, and 
+$\Sigma\lambda_D$ the total number of dangerous base component failure modes.
+
+$$ DiagnosticCoverage = \Sigma\lambda_{DD} / \Sigma\lambda_D $$
+\end{frame}
+
+
+\begin{frame}
+The diagnostic coverage for safe failures, where  $\Sigma\lambda_{SD}$ represents the percentage of
+safe detected base component failure modes,
+and $\Sigma\lambda_S$ the total number of safe base component failure modes,
+is given as
+
+$$ SF = \frac{\Sigma\lambda_{SD}}{\Sigma\lambda_S} $$
+
+
+\textbf{Safe Failure Fraction.}
+A key concept in  FMEDA is Safe Failure Fraction (SFF).
+This is the ratio of safe  and dangerous detected failures
+against all safe and dangerous failure probabilities. 
+Again this is usually expressed as a percentage.
+
+$$ SFF = \big( \Sigma\lambda_S + \Sigma\lambda_{DD} \big) / \big( \Sigma\lambda_S + \Sigma\lambda_D \big) $$
+
+\end{frame}
+
+\begin{frame}
+ SIL Levels are how they are calculated
+\end{frame}
 
 \section{FMEA - General Criticism}
 \begin{frame}
@@ -347,8 +402,9 @@ and allows diagnostic mitigation for self checking etc.
   \pause \item FMEA type methodologies were designed for simple electro-mechanical systems of the 1940's to 1960's.
 \end{itemize}
 
-FMEDA is an extension of FMEA, in that it will give higher ratings
-for self checking. It
+FMEDA is a modern extension of FMEA, in that it will allow for 
+self checking features, and provides detailed recommendations for computer/software architecture,
+but
 
 \end{frame}