We primarily recommend using rechargeable batteries.
You can temporarily use non-rechargeable batteries, but then THE BATTERIES CANNOT BE CHARGED! RECHARGING NON-RECHARGEABLE BATTERIES WILL CAUSE A DANGEROUS SITUATION / HARDWARE FAILURE!
CAN I USE FOUR WIRELESS MICROPHONES AT THE SAME TIME?
Yes you can, only if the frequency between all the mics are different. The Wireless Microphone Set U-TUBE 20 comes in two different frequency pairs; 864,900 MHz / 863,100 MHz and 863,550 MHz / 864,300 MHz