A b&act A versatile lattice for a tau-charm factory working at 4 GeV center of mass energy with 1O33 cm-' s-l luminosity is considered in this paper. The main goal of this study due to absence of experience in this kind of features, is the possibility to use easily the same lattice for either monochromatization (low-emittance) scheme or standard (high-emittance) scheme. This monochromatization scheme permits to reduce the spread of collision energies at the interaction point to the level of 0.1

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... MeV. In this paper we consider a low-emittance arc (lo-' m rad) typical from synchrotron radiation lattices and the passage from low-emittance to high-emittance (10B7 m rad) is obtained by detuning of the low-emittance arc.