The COM-2B Series crossover manifold system uses two PR-1-type stainless steel regulators (PR-2-type brass, optional) built in a single body functioning as the changeover regulators with the common outlet port connected to a single line regulator to provide constant unchanging supply pressure unaffected by supply source depletion. All are mounted on a bracket complete with gauges. As the primary supply source depletes and the operating outlet pressure of the primary regulator falls below the preset changeover pressure of the secondary regulator, the secondary regulator takes over. Once this occurs, the primary regulator can be manually adjusted 1⁄8-turn counterclockwise, the secondary regulator is now the primary and the depleted supply source can be replaced.