The HM-21 from Lectrosonics is a digital hybrid plug-on UHF wireless transmitter. It enables you to transmit the signal of a microphone or a line-level source wirelessly. The HM-21 overcomes inherent channel noise with its patented hybrid technology, which digitally encodes the audio. A Lectrosonics digital hybrid receiver will decode the audio, giving the user all of the benefits of conventional FM wireless systems (range, resistance to interference, etc.) without the noisy artifacts introduced by analog compandors.

Owning a Lectrosonics digital hybrid receiver isn't absolutely necessary with the HM-21. It's backward compatible with 100, 200, and IFB series receivers, as well as being compatible with analog receivers made by other manufacturers. Phantom power from its standard XLR input jack is selectable between 5, 18 and 48 volts, making the HM-21 compatible with just about any condenser or dynamic microphone. It will run on two readily available alkaline AA batteries for 4.5 hours, or up to 12 hours with lithium.

The sound quality of the HM-21 transmitter is outstanding. The power supply provides constant voltages, switching to accommodate the life-cycle of the batteries, resulting in an ultra low noise input amplifier. It features a DSP controlled limiter that can handle peaks over 30 dB. The excellent signal to noise ratio and dynamic range of the HM-21 qualify it for use in the most demanding of professional applications.