 Component quotient of the real Lorentz group in two dimensions

Let $B(x)=\left(\begin{array}{cc}\cosh x& -\sinh x\\ -\sinh x& \cosh x\end{array}\right)$, $T=\mathrm{diag}(1,-1)$ and $P=\mathrm{diag}(-1,1)$. Every real matrix preserving $\mathrm{diag}(1,-1)$ has a unique form $B(x)S$ with $S\in \{I,T,P,TP\}$. The boost subgroup is normal because $TB(x)T=PB(x)P=B(-x)$. Its four cosets form the Klein four-group, giving the displayed quotient group. In contrast, the four-element subgroup generated by $T,P$ is not normal: $B(x)TB(-x)=B(2x)T$ is not diagonal for $x\ne 0$. This distinguishes the normal identity component from a chosen set of component representatives.