Dictograph

• (n.) A telephonic instrument for office or other similar use, having a sound-magnifying device enabling the ordinary mouthpiece to be dispensed with. Much use has been made of it for overhearing, or for recording, conversations for the purpose of obtaining evidence for use in litigation.
Found on http://thinkexist.com/dictionary/meaning/dictograph/

Dictograph

Dic'to·graph noun [ Latin dictum a thing said + English -graph .] A telephonic instrument for office or other similar use, having a sound-magnifying device enabling the ordinary mouthpiece to be dispensed with. Much use has been made of it for overhearing, or for recording, conversations fo...
Found on http://www.encyclo.co.uk/webster/D/61
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