A dictaphone was a device which recorded sound.
Jamie McCrimmon was fascinated by gadgets such as Polly's secretarial dictaphone, on which she kept his recordings for many years after their travels. (AUDIO: The Forbidden Time)
In 1969, the Tenth Doctor recorded an alien signal at Mission Control with a dictaphone, and then was arrested. After the Doctor escaped several days later, he used the TARDIS to translate the recording into a visualisation of the sounds so he could communicate with the aliens. (PROSE: Blue Moon)
While discreetly working to undercut the Rutans, the Third Doctor gifted Sarah Jane Smith with a dictaphone which was made in Taiwan, 1997: her future. Later, Brigadier Lethbridge-Stewart brought it through a time tunnel to the Rutans' ship, where it was destroyed.
In the end, Sarah suggested that the Doctor did this in order to clue her in to the Rutans' clearly false story about a Sontaran invasion in 1994. (AUDIO: The Children of the Future)
Ben Anderson, a travel writer, used a dictaphone while sailing on the Neptune. (PROSE: Dateline to Deadline)