Created through the manufacturing trees of craftsdwarves, metalsmiths, and mechanics.
The craftdwarves construct components from the smithed metal parts that are ready to be used for such detailed and complex parts. The mechanic assembles the components and installs the Klaxon.
Klaxons/voiceboxes would be triggered to pressure plates, also certain nobles would demand them for broadcasting orders and announcements. Klaxons can wake dwarves from sleep and help assemble a militia or army quicker, but they will obviously have negative effects if they wake other dwarves.
Voiceboxes could be set to say a phrase you can pre-set. This might not be useful for dwarves (although maybe you could drive nobles insane with hidden voiceboxes that constantly whisper words of demons, madness, and blood) but you could construct an elaborate notification network of voiceboxes and plates, setting each voicebox-plate pair to say something appropriate to the area as a normal game announcement:
Ex: Something is coming through the northmost chasm gate!
Something is between the northmost chasm gate and the barracks!
It could also say something completely random, or "Tostitos is AWESOME." If you've ever messed around with the quake games and level editing, you know the concept of triggers. These voiceboxes could give hints to adventurers travelling through your fortress in much the same way.
Klaxons can be triggered to 'warn' dwarves of various things- warn dwarves to exit a designated area, warn dwarves to stay off of a certain bridge (multiple can be linked), etc.
Enough klaxons per dwarf would enable the setting of one task as a priority task for everyone with it enabled- "HAUL FOOD BEFORE ANYTHING ELSE" / "HAUL STONE" etc, without micromanaging their labor list.
[ June 10, 2007: Message edited by: Tostitos ]