The wireless bodypack shall be a professional transmitter for audio signals with switchable carrier frequencies as well as preprogrammed groups with up to 12 compatible channels. An infrared signal shall be used to synchronize the frequency between transmitter and receiver. 
The transmitter shall send a tone key (32.768 kHz) to provide improved operation reliability and prevent switching noises. The audio signal should be muteable. 
The transmitter shall have a 3-position input attenuator (+15, 0, -10 dB), a timed backlit LCD showing a frequency group and channel, battery strength and locked/unlocked status. F
requency and power locking capability shall be included.

Technical Specifications 
Carrier Frequency: 518 - 865 MHz (available frequencies depend on applicable country regulations)
RF Output Level: 10 - 30 mW (dependent on frequency version)
Battery Life: at least 8 hours (with 2 AA alkaline batteries)
Overall Dimensions (HxWxD): 108 x 64 x 19 mm (without antenna)
Net Weight: 81 g (without batteries)