VPU Mic / Voice Projection Unit Microphone – For Avon M50 Gas Mask / Respirator Avon Protection Systems – part#. VPU Microphone (gray) Highlights. Advanced / Ultra-Compact Design. Intrinsically Safe – (Rated for use in environments filled with combustible gas / explosive hazards). Plugs in to the M50 interior ECP / Electronic Communications Port located inside the M50 facepiece & interfaces with the externally mounted VPU (Amplifier) which plugs into the outside ECP. (The VPU is required, we have a set listed with both the VPU & Mic if you don’t already have the VPU, Avon p/n 71009/2). This incredibly small mic significantly improves clarity of speech. Amplifies barely audible sounds such as speaking in a soft voice or even a whisper! The mic connects via the internal ECP (electronic communication port) & passes clean & undistorted sound through to the VPU Voice Projection Unit / Powered Gasmask Amplifier which connects externally to the M50 / M51 respirator. Normally, a gas mask that is not equipped with the optional VPU unit, allows speech to pass through the facepiece material via the mechanical voice emitter membrane. That system works, however it is far from perfect. Masks equipped with the (very cool looking) VPU unit amplify that sound so that it can be heard in noisy environments. In particular its useful for crowd control, riot control operations, but could prove invalueable in any emergency situation. Additng the mic unit to the M50 gas mask thats already equipped with the external voice amp (VPU), allows for faint sounds like a whisper (from user) to be amplified by the VPU perfectly, with zero distortion from the mechanical voice emitter membrane (the distortion is minimal, however, when speaking in a normal voice as the mechanical membrane/voice emitter works best when speaking in a normal voice or louder). For these reasons, the mic & VPU add to the overall clarity of a users voice. Lastly, for professional users (such as law enforcement & military users), needing to communicate thru comm systems (police radio or military comms), there is an additional piece available’comm adapter’ (black) piece that enables that functionality. Most users do not require the 3rd piece as its only for connection to an external comm system. (We also have those available). The mic & VPU are intrinsically safe & therefore can be used in combustible environments or areas that could pose an explosion hazard. The VPU & Mic both conform to UL Standard 913, Class I, II, III Div. 1 GR A-G, T4, Control DWG 17478. The Avon VPU uses 2x AAA batteries, from which the mic draws power, so no additional batteries or wires are needed. The M53, FM53, C50, M50 & M51 all have the connections built-in via ECM port(s). NOTE: The PCM50 / PC50 does not have these features. Other listings of interest. For users who need BOTH the VPU & Internal Mic Assy (Gray Piece), please see listing# 302315720438 (for the 2 piece set). Information deemed accurate but is not guaranteed.