Portable Detective Dictograph Audio Amplifier, 1907

The Portable Detective Dictograph Audio Amplifier from 1907 was made by General Acoustic Company, Jamaica, New York and invented by one K. Monroe Turner. This is one of the first audio amplifiers. Ads placed in law enforcement and private detective trade journals (of which there were very few at the time) claimed this this unit could be installed and hidden just about anywhere. You know, under "rugs" and "beds". This state-of-the-art equipment of it's time sold for about $125.00. Remember that the average salary in America at that time was about $750.00 a year. That means that this unit cost about two months pay. The units could be rented for about $6.00 a month.

The Detective Dictograph Kit came with headphones (right top), regulator (left middle), a box
microphone (left top) and a round microphone (lerft bottom)

This was such a popular product that the federal government ordered so many of them, Turner's little company was hard pressed to keep up with demand. For a while, they became hard to obtain. In 1910 a model called the Detective Dictograph was offered and sales skyrocketed again. The famous private detective Burns used the product to solve many otherwise unsolvable cases by having the “mechanical ear” planted in prison cells and private rooms. Eavesdropping at the time was not illegal.

Instructions for using the Detective Dictograph that was inside the top lid of the black box.

An early photo of a man using the detective dictograph in a law office.

An early photo of the microphone of the Detective Dictograph hidden under a desk

Read An early Four Page Article Titled: What Is A Dictograph

To read more about the history of the Portable Dictograph, click here.

From The Ralph D. Thomas PI Vintage Collection
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