If the cable is not in a duct, $Do_d$ is equal to the cable outer diameter $D_e$.

Symbol
$Do_{\mathrm{d}}$
Unit
mm
Used in
$A_{\mathrm{d}}$
$L_{\mathrm{deep}}$
$L_{\mathrm{psc}}$
$T_{\mathrm{4et}}$
$T_{\mathrm{4ii}}$