The Azden WHX-PROS Wireless Microphone System is designed for Professional videographers on a limited budget or video hobbyists. The "PRO" Series are 2-channel switchable VHF systems that allow you to switch to the other channel if one is being used, or is noisy. All receivers and transmitters in the "PRO" Series are on the same 2 frequencies and use the same circuitry, making them interchangeable, and allowing you to add to your system at any time. The range is more than 200 feet.
This WHX-PRO "S" System has the same features as the WHX-PRO system, except it uses two completely different frequencies. The purpose of this is to be able to use 2 systems at the same time without experiencing interference.