S.D. Codified Laws § 9-41-7
There shall be a statutory mortgage lien upon the improvements, expanded or reconstructed telephone plant in favor of and for the equal benefit of the lawful holders of said bonds and interest coupons, and each of them, but no such lien shall attach to or become a charge upon or against those portions of the municipality's telephone lines or facilities which were not improved, expanded, or reconstructed with the proceeds of the revenue bonds. Until all such bonds are fully paid with interest, the municipality shall not sell or otherwise dispose of its improved, expanded, or reconstructed telephone lines or facilities and shall not establish, authorize, or grant a franchise for the operation of any other telephone company for furnishing exchange telephone service in competition with the municipal telephone lines and facilities within the municipal limits.
SDCL 9-41-7