Click for homepage
Optics
Free space optics · FSO - under construction

This section of the website covers a wide range of optical and opto-electronic (optronic) devices that were used in covert operations, ranging from infrared communication devices (photophone) to long-range motion detection systems. Such devices are also known as Free Space Optics (FSO), and can be active as well as passive. This section is currently under construction.

Optical devices on this website
American infrared transceiver XE-2, developed in the mid-1950s.
Infrared transceiver (Lichtsprechgerät) 'Dahme 1'  developed in the DDR
Infrared transceiver (Lichtsprechgerät) 'Dahme 2'  developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4 developed in the DDR
Passive infrared communication device
Infrared transceiver (Lichtsprechgerät) JO-4.02 developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4.03 developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4.05 suitable for transmitting video
Infrared transceiver (Lichtsprechgerät) JO-4.06 suitable for receiving video
Modular infrared transceiver (Lichtsprechgerät) developed in the DDR
LED research project
ALD
Covert infrared telephony
Covert cameras
Covert lenses
Photophone   Lichtsprechgerät
Free-space optical communication

A Photophone is a speech communication device that uses a light beam for the transmission of voice conversations, invented in 1880 by Alexander Graham Bell in the USA. As light propagates in a straight line and can be obstructed by objects in the transmission path, it is basically a line-of-sight communication device. In the German language it is known as a Lichtsprechgerät. 1

The Photophone invented by Alexander Graham Bell

The Photophone was invented by Alexander Graham Bell 2 in the USA, the same man who had invented the telephone a few years earlier [1], and was first demonstrated on 3 June 1880 [2]. It used a light beam to transmit audio over a distance of 700 feet (~213 metres). Although there was no immediate practical use for it at the time, Bell would later call it his greatest invention.

The first practical implementations were developed during World War I (WWI) and World War II (WWII). The German manufacturer Siemens & Halske developed a device for the German Navy that could be used over distances of more than 8 km by using current-modulated carbon arc lamps.

During WWII, the German Army made practical use of optical transmission, with Lichtsprechgerät 80, a device that was developed in 1935 by the Carl Zeiss optics company and that allowed line-of-sight communication over a distance of up to 5 km. In the years following WWII — during the Cold War — several types of photophones were developed in the former DDR (East-Germany) for virtually undetectable covert communication across the East-German sector and state borders.

The Photophone can be seen as the precursor to the fibre-optic communication systems that became popular in the 1980s and that are now used as the backbone of our modern era internet.

  1. Literally translated: light speech device.
  2. Jointly with his assistent (and later associate) Charles Sumner Tainter.

Free-space optical communication on this website
American infrared transceiver XE-2, developed in the mid-1950s.
Infrared transceiver (Lichtsprechgerät) 'Dahme 1'  developed in the DDR
Infrared transceiver (Lichtsprechgerät) 'Dahme 2'  developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4 developed in the DDR
Passive infrared communication device
Infrared transceiver (Lichtsprechgerät) JO-4.02 (Palme) developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4.03 developed in the DDR
Infrared transceiver (Lichtsprechgerät) JO-4.05 (Palme) suitable for transmitting video
Infrared transceiver (Lichtsprechgerät) JO-4.06 (Palme) suitable for receiving video
Modular infrared transceiver (Lichtsprechgerät) developed in the DDR
LED research project
ALD
Covert infrared telephony
Four generation of Stasi IR-transceivers

Known Stasi optical communication systems
Model Project Codename Description Origin Range
? ? Dahme 1 IR set, base unit OTS 3 km
? ? Dahme 2 Concealed as camera OTS 2 km
JO-4 17305 Neue Dahme Small IR set CZJ 3 km
JO-4.01 17303 ? Passive IR set CZJ 500 m
JO-4.02 17304 Große Dahme Large IR set CZJ 5 km
JO-4.03 17305-1 Kleine Dahme, Palme Small IR set CZJ 3 km
JO-4.05 ? ? Video transmitter CZJ 1.5 km
JO-4.06 ? ? Video receiver CZJ 1.5 km
? 17312 Finow I Miniature set CZJ 2 km
? ? Finow II In binoculars OTS ?
? ? ALD-3K Covert telephony INT 2 km
 About the Stasi


Related patents
Nomenclature
  • Photophone
  • Lichtsprechgerät (German)
  • Optical communication device
  • Optical transceiver
  • Light-based transmission
  • Infra-red transceiver
  • IR transceiver
  • Lumofon
  • Optophone or Optophon 1
  1. This name is also used for an acoustic reading aid for the blind.  Wikipedia

References
  1. Wikipedia, Alexander Graham Bell
    Visited 27 October 2021.

  2. Wikipedia, Photophone
    Visited 27 October 2021.

  3. Wikipedia, Free-space optical communication
    Visited 22 November 2021.

  4. Peter Greil (DL7UHU), www.lichtsprechen.de
    Visited 22 November 2021.
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Wednesday 27 October 2021. Last changed: Monday, 20 December 2021 - 10:14 CET.
Click for homepage