Extrinsic curvature of a curve

Question

I have a simple question. Curve in ${R}^{1,1}$ The 2 dimensional Minkowski space. \begin{equation} \gamma:[0,1] \longrightarrow R^{1,1}, \end{equation} How can I calculate the extrinsic curvature of this curve seen as a 1 dimensional surface embedded in $R^{1,1}$?

Thanks!