AKG WMS40 Pro Vocal Dual wireless system with twin-receiver, 1 fixed frequency (864.375MHz/864.850MHz), 2x HT40 Pro hand-held transmitters, up to 30 hours' use with 1x AA battery, 2x SR40 Pro non-diversity receivers in single metal housing, 1/4 jack output. Includes stand, batteries and power supply. Available in 3 different frequency pairs, up to 2 parallel systems.