The World Wars - Government Surveys its People
During World War I, President Woodrow Wilson and the FBI monitored dissent for the war in the U.S. One of the targets they were particularly concerned about was socialist leader Eugene V. Debs.
The Dictaphone Corporation released a phonograph-based recorder that was able to record telephone lines with reliability. At the time, AT&T did not allow the use of this device on its public lines, although it was permitted to be used by power companies and railroads for their private lines.
During WWII, magnetic tape was used by the Nazis to conduct surveillance operations. The Magnetophon was developed by AEG, a German electronics company who had purchased patents from Thomas Edison for his work on the phonograph.
At the same time, the U.S. government monitored telephone and cable transmissions between the U.S. and Japan, as well as the Japanese Americans whom they had placed in internment camps. The House of Representatives had held hearings regarding whether wiretapping was legal in the case of national defense. Most of the legislation and court decisions that took place before WWII had strictly limited the ability of the U.S. government to wiretap citizens. However, in the advent of World War II, the importance of national security weighed heavily on the legislators.
On a more local scale, the police and detectives used electronic devices like The Dictagraph (sometimes spelled Dictograph) for their work. The Dictograph had a highly sensitive transmitter, which allowed it to record conversations from a distance (most other devices at the time required the speaker to be a few inches from the recorder).
The Dictograph. It was more portable than earlier devices and was extremely sensitive, which made it ideal for recording conversations by detectives and the police.