In the present paper, the properties of a locally compact Hausdorff topological Brandt semigroup, and the relation between its semigroup algebras and ℓ1-Munn algebras over group algebras are investigated. It is proved that for each locally compact Hausdorff topological group G, and each index set I, there exists a locally compact Hausdorff topological Brandt semigroup S=B(G,I) such that the Banach algebras \documentclass[12pt]{minimal}
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\begin{document}$\mathcal {LM}_{I}(M(G))$\end{document} and \documentclass[12pt]{minimal}
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\begin{document}$\mathcal{LM}_{I}(L^{1}(G))$\end{document} are isometrically isomorphic to M(S)/ℓ1({0}) and Ma(S)/ℓ1({0}), respectively.