Output Devices

Information can be transmitted by wireless technology in various ways, depending on the type of transmission different devices are used for output intelligible to human ears or eyes.

Morse code telegraphy

In the early days of wireless and even wired communication, messages were sent in the form of Morse code. Of course, the signalmen operating the earliest wireless sets, the soldiers of the „Spark Companies“, had to be trained in using the manual morse key to transmit and to record Morse code transmissions by ear.

This was not a problem, as long as only professional radio operators and radio amateurs were trained as signalmen; they mastered the Morse code in sleep, almost as well as foreign language skills.

With the spread of the importance of wireless communications, the need for signalmen able to work with morsecode has been growing. The Armys epectations have not been met by militia radio operators in many cases.

Thus, there were ideas to simplify the transmission of telegrams with technical means, so that Morse code training was no longer necessary for all signalmen.

It turned out, that High speed telegraphy would not meet the requirements. With high speed telegraphy systems, messages could be transmitted in high speed morse code easily. But these had to be printed to paper, and then decoded in a tedious way from the Morse code to letters. If the operator's Morse code knowledge was poor, this step of reading and decoding the Morso code paper tape stripes needed as much time, as direct Morse code reading from the headphones. So this procedure was abandoned after a few years, and more effort was placed on the Morse training, after it turned out, that highly trained telegraphists could read by ear nearly as fast as high-speed Morse code transmission.


The use of wireless transmission became much easier, when radio telephony was available. In the case of AM or even single-sideband transmissions, propagation disturbances affect communication quality much more than the use of frequency-modulated sets, which became standard after the shift of military radio communication into the VHF band after World War II.

In the early years, people often worked with headphones and a hand-held microphone. Later on headsets were in which hands were free, a throat microphone which did pick up less ambient noise, and earphones which could be worn under the helmet, were introduced.

In Switzerland quite often, microphone-handset combinations were commonly used. They look like a telephone handset with an integrated push-to-talk key, in Switzerland these were commonly referred to as Microtel or Microtelephone.

Without a hard-to-crack voice scrambling or speech encryption, the drawback of telephony was, that transmission could easily be intercepted - stickers „Watch out, enemy is listening!“ pointed this fact out to the military users.

Only with the introduction of digital technology it was possible to realize effective speech encryption even for telephony connections with comparatively simple effort.


Even in the early years in the history of electronic communications, engineers tried to find ways to transmit important information not as spoken words, which one had to write down for the afterworld, but to send written text, so that recipient could read the content at any time.

Thus, telegrams were initially transmitted with Morse code and written down by the telegraph operator on telegram forms. There were early attempts made with telegraph systems which either were technically unreliable or needed to many wire connections between sender and receiver site.

A major development step was the introduction of the teletypewriter: In the thirties, a wired teleprinter service was developed, in Germany in 1933 a telex service using a self-dialing network was installed. The teletype machines communicate with each other via a defined protocol. The Baudot code with 5 data bits is used, the usual communication speed is 50 baud (later machines could be converted to 75 baud with special gearwheels).

As a successor to the antiquated Morse telegraph printers in use since the late 19th century, the Swiss Army in 1934 made a decision to intruce the in those years quite advanced „printing telegraph“ Siemens T. type 34, the material housed in eight crates, however, was heavy and bulky.

As an alternative to the expensive and mechanically intricate teletypewriter, Dr. Ing. E. Gretener developed a printing telegraph system on his own initiative, the so called „ETK“ (One tone combination printer). The transmission method is based on a unique 14 segment code. In contrast to Baudot code CCITT No.2, in which even the failure of one character or bis (for example, in a disturbed radio transmission) is leading to mutilation of the complete message following, a text printed with the 14 segment code can usually be deciphered even in case one or another segment is left out.

The ETK was initially used on wired telex connections, only the improved veriant ETK-R (Model 55) with improved filters allowed to use wireless transmission with an acceptable quality.

Hell Printer

In order to cope with the problem of faulty and slow message transmission by poorly trained telegraphists, the Siemens Hellschreiber system was acquired from 1936 to be used on the high power stations for nationwide connections.
Since the requirements for the signal coming from the receiver to drive the Hell printer and for the signalmen operating the receivers were even higher than for the CW reception, the receivers initially used ( Lorenz EO 509/1 in the G1,5K Station) turned out to be unsufficient because of inadequate sensitive, first the receivers hat to be exchanged for a superhet model (Zellweger E41) and shortly after, the Hellschreiber equipment was completely removed from the stations and replaced by the High Speed Telegraphy System Moser-Baer.

For use on long-wave connections and wired communication, the method „Hell“ proved enough reliable and remained in use until around 1950, when the ETK could be procured.

Cipher Equipment

In military communication, for centuries it has been a concern to send messages to their own troops, which, if intercepted by the enemy, are incomprehensible to them, and that no information can be extracted from messages intercepted by enemy forces.

In ancient times, written messages were encrypted; on the other hand, every side tried to catch enemy messengers and to elicit the information from them. Since the 19th century, simple encryption methods which rely on a mechanical or paper-based encryption tool, have been developed.

Basically, the situation changed with the introduction of cipher machines, the most famous of which, the German cipher machine Enigma was developed by Arthur Scherbius in the 1920s and went into regular production by the Berlin company Heinsoeth and Rinke.

In Switzerland, the commercially available Enigma K was used for encryption initially. During the years of the World War,after it turned out, that both sides, the Axis and the Allies, were able to decode encrypted messages, the cipher office of the Swiss army, together with Zellweger, developed the „Ne(w) machine“ NeMa which became the backbone of offline encryption for many years.

A stroke of luck for Switzerland was the move of Boris Hagelin from Sweden to Switzerland in 1948. Together with Dr. Ing. Edgar Gretener, who had developed the teletypewriter ETK, they worked on the development of automatic cipher machines. The Telekrypto 53 and especially the KFF 58 were breakthroughs in automatic encryption.

With introduction of modern digital technology, encryption technology has become easier to handle and easier to implement in digital communication systems; the modern encryption technology has lost much of the charm of the machines with the rattling gears and cipher wheels.

A simpler way of making a voice transmission unrecognisable is voice scrambling with chopping fragments of a voice transmission in rearranging them in a different order, when reassembled in the correct order after transmission, the voice information can be made audible again. The cryptological security is lower than with character encryption, but it is sufficient to make message content unrecognisable in a tactical context.

Work began in Switzerland with the „Chiffrator“ MV22 voice scrambling device, BBC worked on this set after 1956. It never reached field use maturity, but the technology developed was later used in the Vericrypt 1100, SVZ-226 and SVZ-430 voice scramblers.

Personal Computer

In the late 1990s, the noisy and rattling teletypewriters had to be replaced with the introduction of the SE-430. The combination of teletypewriter and TC-61 was replaced by the the Telematikset 430 and Telekrypto 535.

For electronic communication, a set compiled by RUAG with a notebook computer and a dot-matrix printer in a NEMP-secured case was used.

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en/endgeraete.txt · Zuletzt geändert: 2024/01/15 08:35 von mb