Dictograph Among the earliest covert listening devices used in the United States of America was the dictograph, an invention of Kelley M. Turner patented in 1906 (US Patent US843186A). It consisted of a microphone in one location and a remote listening post with a speaker that could also be recorded using a phonograph. While also marketed as a device that allowed broadcasting of sounds, or dictating text from one room to a typist in another, it was used in several criminal investigations.
DictOgraph among ThE eArLIeST CoVeRt lIsteNinG DEvices USeD in thE UNiteD stATeS Of amerICa Was tHe Dictograph, an inventIon oF kElleY m tURner PatEnted In 1906 (US PAtEnt us843186a) it consistEd of a miCroPhOne in onE loCatiON and A remOte listeNIng pOSt with a sPeAKer thAt cOulD aLsO be RECOrdeD using a phoNogRaph. WhilE aLsO mArKeTeD aS a DEvICE THAT ALLowEd bRoAdcastIng of soUnDS, oR dicTating Text from ONe roOM To a typist iN aNOther, It was UseD iN seVeraL CrImInal iNvEstigaTioNs