RC-1 Retard Chamber is required in installations that will be subject to pressure variations, as are generally associated with public water supplies, in order to help prevent false alarms. The RC-1 is specifically intended for use as a separately ordered item for the Model AV-1-300 Alarm Check Valve (TFP910). It can, however, also be used as a separately ordered item for changing out older style Retard Chambers used with the Central Model F/G, Gem Model A, or Star Model E/F Alarm Check Valves.