The Walkie-Talkie is an item that is added by Mekanism and can be used to communicate using voice through a Minecraft server. It has eight different channels (1-8).
By right-clicking while sneaking, the Walkie-Talkie can be turned on or off.
By pressing the Mekanism mode-switch key (default M), the channel on the Walkie-Talkie can be changed from one to eight.
By holding the Mekanism voice key (default U), the Walkie-Talkie will begin transmitting the player's voice to other Walkie-Talkies on the same channel.
If desired, the voice server functionality can be disabled through the
VoiceServerEnabled option in the Mekanism configuration file.