You select you frequency by unscrewing a cap that releases a cover, exposing a pair of rotary switches. Any pack can be set to an impressive 256 frequencies, each in 100kHz steps over a 25.5MHz range. That’s some serious flexibility. The unit is powered with one AA battery, which is inserted by unscrewing the largest metal cap, which sticks off the bottom of the pack a little. Using a lithium battery, Lectrosonics claims a 5.5 hour battery life. Lithium is recommend, as duration drops sharply with a NiMH battery (4.5 hours) or an alkaline battery (a measly 1.5 hours). The unit is powered on and off by an interesting magnetic switch that eliminates the requirement of a physical connection between the switch control and the actual switch mechanism, which keeps this unit water-tight. However, since Lectrosonics shows you how to replace this switch in the manual, I imagine it’s somewhat easy to lose.

On the top of the transmitter, there’s a permanently attached antenna and a audio level knob (ie, gain). Clearly, if that knob changes either by accident or on purpose, you’ll be thrown a curve ball at front of house. Other manufacturers go to great efforts to conceal this secret knob. The microphone element connects using a 2.5mm Microjack.

The MM400c is designed to work with the Lectrosonics 400 series receivers, which are all Digital Hybrid receivers. However the MM400C unit is backward compatible and, using the Compatibility Mode, you can configure the transmitter to work with the 200 and 100 Series of Lectrosonics receivers, as well as some receivers from other manufacturers.

The MM400c is a tough nut. I don’t know if it makes complete sense to specify as a regular old mic pack, but any time water is in your production design, I’d demand an MM400c and watch it go into combat.