In this article, a collaborative observer is proposed for a class of Linear Switched Systems affected by unknown inputs. The class of switched systems under study accepts a dwell-time and has a completely known exogenous switching signal. Two main elements compose the proposed observer: a point observer designed using High-Order Sliding-Modes, which provides finite-time exact convergence in the presence of disturbances with a time-varying known upper bound, and a collaborative observer that gives an interval estimation of the state in the presence of the unknown inputs.