Dictograph - Set for hidden listening to conversations.
Produced in 1907 by "General Acoustic Company, New York,
USA". The oldest exhibit my collection, and holds a
special place. Despite its venerable age, everything is in good
working condition . suitcase outside for 100 years, of
course shabby, but inside all preserved in almost
perfect form. Surprisingly excellent state of the wires,
because they usually wear out first. It is well
preserved as the original description of the scheme
included. The kit consists of two different
constructions of microphones, headphones with two
holders, the switch with stepped volume control, and a
set of connecting wires with lugs, different length and
destination. All this is packaged in a wooden suitcase
lined with leatherette. Outside there is a leather
handle and a steel lock with a hole for the key.
Dimensions 335 x 200 x 85 mm. Weight kit assembly 2.3
Photos can be enlarged
Detective Dictograph was the first mass-production for
covert listening device, and use them at the time could
anyone, from detectives and security services to
individuals, because the law does not prohibit. The
restriction was only a mere possibility of owning it,
because its price was high. With average annual earnings
of $ 750, it cost $ 125, representing a two-month
earnings of the average American. It was also possible
to rent it for the price of 6 $ per month.
The principle of the device is well understood from the
scheme. The battery feeds the chain microphone -
earphone, among which included a switch with stepped
volume control. This standard battery "General Acoustic
Company" of little more than 15 minutes of operation.
Nevertheless, for 1907 it was very technologically
advanced and invention. Its author is K. Monroe Turner.
Using the device was pretty simple. For example, to
listen to the neighboring room, had to hide in one of
its microphones, and connect its long wire with a switch
in another room. To switch the jacks connected earphones
and battery. Range is naturally limited by the length of
the wire. The set has two shuttles with long wires 10
and 20 meters.
One of the microphones, a rectangular shape, made of
Bakelite, has a resistance of 500 ohms, dimensions 85 x
85 x 25 mm and weighs 135 g. One side of it there is an
inscription "Turner Dictograph", while the other is
information about the manufacturer and patent - "General
Acoustic Company Jamaika, New York City Made in USA.
Patented Feb.5.1907 Feb.19.1907 Dec.17.1907 Other
Patents Pending ". In the upper face of the available
sockets for connecting wires, and next to them screwed
ring for mounting on a vertical surface. Second
microphone, in a round metal casing, has a resistance of
500 ohms, dimensions 58 x 20 mm, and weighs 70, at the
rear side of the screwed connection jack, and a ring for
Switch circular has dimensions of 68 x 20 mm and weighs
90 g. nor any other labels, but labels terminals, it is
not. In a stepped volume control used wire resistors
overall resistance of 50 ohms. The photo can be seen
spirals of wire without a skeleton.
Both headset of the same design, but have different
resistance windings, 11 ohms and 15 ohms. Apparently
this error in production. Otherwise, they are absolutely
the same, have a metal housing with a switch on the back
side. Diameter 58 mm, Thickness 24 mm, weight 130 g. In
a set there are two sets of wires to connect the
headphones. One is designed to ensure that both headsets
used one man, the second allows you to spread the
headphones at distances up to 1,5 m items in suitcase
distributed offices, and a headphone is a separate box.
Microphones are placed in a rectangular compartment, one
above the other and separated by a rectangular carton
with the tongue of the tape. In the upper lid of the
suitcase inside is also a Reed, pulling that can open an
office in which to store a description of the scheme
included. On the cover of the office marked embossed
gold inscription "The dictograph patented. Sold and
licensed for use in accordance with conditions and
restrictions of sales agreement ".
Of course it is understandable that in 1907, this is not
the Stone Age, and even then there were some serious
technology, but nevertheless, the thing is impressive,
including the fact that it was made 100 years ago.
photos showing the use Dictograph