The Sennheiser XSW 1-825 Dual bundles great sound and ease of use into a sleek handheld wireless system. The two included transmitters employ 825 cardioid capsules with a warm, smooth sound and excellent feedback rejection. Convenient features like one-button scanning and synchronization are housed in a streamlined receiver with built-in antennas. Intuitive icon-based indicators make operation a piece of cake. Use up to 10 systems simultaneously. The Sennheiser XSW 1-825 Dual is a great handheld wireless system for singers, presenters, and instrumentalists.

Wireless dual vocal set. Includes (2) SKM 825-XSW handheld transmitters with mute switch and e 825 capsules (cardioid, dynamic), (1) EM-XSW 1 DUAL stationary receiver with internal antennas, (2) MZQ 1 microphone clips, (1) NT 12-5 CW power supply and (2) pairs AA batteries, frequency range: B (614-638 MHz)

• Excellent live sound featuring Sennheiser's renowned evolution microphone capsules (e 825)
• Antenna-switching 2-channel diversity reception
• Integrated antennas
• Automatic frequency management and synchronisation via remote channel for easy setup
• Selectable UHF frequencies within a large bandwidth
• Up to 10 compatible channels
• Excellent live sound featuring Sennheiser's renowned evolution microphone capsules
• Antenna-switching 2-channel diversity reception
• Integrated antennas
• Automatic frequency management and synchronisation via remote channel for easy setup
• Selectable UHF frequencies within a large bandwidth
• Up to 10 compatible channels

Choose the Wireless Frequency correctly 

> Wireless Audio Devices Guide - by Department of Infrastructure of Australian Government
https://www.communications.gov.au/what-we-do/spectrum/wireless-audio-devices

> ACMA's Channel Finder - to check what is available in your area
https://channelfinder.acma.gov.au/

> Sennheiser frequency Calculator - to find the best frequency to use in your area
http://www.frequencyfinder.com.au/