The Poulsen wire recorder was used for this by German spies in WWI. If I remember the story correctly -- it was told in a two-part article about the history of magnetic recording in Audio Magazine back in the 1980's -- the spies would record reports in morse code at normal speed and then broadcast them from Long Island at high speed. Early radio experimenters in the US couldn't figure out what that was they'd pick up sometimes. A guy in, I think, New Jersey, recorded onto an Edison cylinder or disk one of the broadcasts, then slowed down the playback and figured out what it was. Authorities were notified and the spy ring was shut down.
Sorry if my memory of the article is mangled, but I think this is the basic story.
-- Tom Fine
----- Original Message ----- From: "joe@xxxxxxxxxxx" <jsalerno@xxxxxxxxxxxxx>
Sent: Wednesday, June 03, 2009 11:47 PM
Subject: Re: [ARSCLIST] Earliest recorded sound update on NPR
data compression ca. 1880
a technique that was not lost on WW1 spies...I wonder if they thought of it themselves or if they knew of this device?
David Breneman wrote:
As I recall, it was a similar disk-based device. The telegraph message would be recorded on it at "human" speed and send down the wire greatly sped up. It was recorded at the receiving end and played back again at the "natural" speed for a telegrapher to transcribe.