A Time-Division Multiplexed (TDM) Hierarchical Switching System (HSS), proposed by Eng and Acampora[5], provides any size of bandwidth for a number of subscribers by allocating proper number of time-slots in a frame. In this paper. Lye present a binary time-slot assignment(TSA) algorithm by which a proper size of time-slots in the frame are allocated to each subscriber so as to meet its bandwidth requests. The time complexing of the proposed algorithm is O(NL loq(2) L) in which N is the number of input/output links of the central switch and L is the number of time-slots allotted to each link in the frame. Rs the authors know. the most efficient algorithm proposed in the literature has time complexity of O(min(L.M-2).min(N,root M).M-2), in which M is the number of subscribers that is larger than N in TDM/HSS system. To give a clear idea of relative efficiency between two algorithms, let us give a typical situation of M = L = O(N-2). In this configuration our algorithm makes a significant improvement in time complexity by the order of O(M-2/log(2)M).