Tennessee Code Title 16. Courts § 16-18-312

(a) If a municipal judge is unable to preside over municipal court for any reason, then a special substitute municipal judge shall be determined pursuant to an ordinance of the governing body of such municipal court. In the absence of such an ordinance, then the municipal judge may designate in writing, to be filed with the clerk of the municipal court, the name of a special substitute judge to hold court in the municipal judge's place and stead. The special substitute judge must meet the qualifications of a municipal judge and the special substitute judge shall take the same oath and have the same authority as the regular municipal judge to hold court for the occasion. Such appointment of a special substitute judge is effective for no more than thirty (30) days, after which a new appointment is required.

(b) Municipal court judges and general sessions court judges are empowered to sit by interchange for other municipal court judges.