We study in this paper local codimension 2 singularities of (first order)
implicit differential equations $F(x,y,p)=0$, where $F$ is a germ of a smooth function,
$p=\frac{dy}{dx}$, $F_p=0$ and $F_{p p}\ne 0$ at the singular point. We obtain topological
models of these singularities and deal with their bifurcations in generic
2-parameter families of equations.