Elcro Family
The Elcro series of crypto equipment is now manufactured by a German company called SIT Gesellschaft für Systeme der Informationstechnik GmbH, a division of  "Rhode & Schwarz SIT GmbH". One of their current products is the Elcrodat 6-2 encryption device together with a host of other security appliances.

Some product lines from the family are:


ELCRODAT Model 4-1D. It was used for bulk encryption of trunks in an Area Communication System called AUTOKO which was produced by Siemens. The device was only used by the 2nd Danish Signal Battalion, as they were they only battalion to use the AUTOKO-system. This was done because their German sister-battalion (610 GE SigBN) in Rendsburg used the system. Both batallions provided a field headquarters LANDJUT Rear (Danish) and LANDJUT Main (German) with communications.

Electrodat Model (?) - Front view.  The crypto unit and the power supply were two separate pieces. (Photo courtesy Royal Signals Historical Collection, Fredericia Denmark)
Electrodat Model (?)  - Power supply. (Photo courtesy Royal Signals Historical Collection, Fredericia Denmark)

elcrodat_6_2 .jpg
Elcrodat 6-2 VOX/ISDN encryption device. (Photo courtesy Rhode & Schwarz )

In some applications, the Electrodat was used to encrypt 10 to 12 Telex lines. Each individual Telex was encrypted with the KW-7 and the Elcrodat was inserted after the multiplexer that combined all The Telex signals. In this instance, the Elcrodat used as superencryption (double encryption) device.


ELCROVOX Model 3-1. It was a narrow-band system used for voice encryption and was used by (at least) 2nd, 3rd and 6th Danish Signal Battalions to provide secure phone lines to their respctive field


Elecrotel - Telegraphy encryption equipment for use on TTY circuits.  Runs up to 1200 baud.

Both the Elcrotel 5 and Elcrovox 1-4D machines looked very similar  Each device consists of two carrying cases, set on top of each other. The bottom one contains the power supply and interface unit while the top one has the cryptographic unit. These devices are keyed by turning the CH/KL (Chiffrieren/Klartext or Cipher/Clear) switch to KL and then inserting a red plastic key into a slot in the device. This key contained a strip of 5-level keytape about 10 cms long. When the CH/KL switch was returned to the CH position, the devices on the circuit, (there could be more than two), quietly went ahead and synchronized. When there was no real traffic to send, the machine continuously generated  "dummy" traffic in order to maintain synchronization and to also confuse any "undesired" listeners.

On RTTY or RVOX circuits, the device had to be manually synchronized by means of a pushbutton, much in the same way as the KW-7.


Elcrobit is data encryption equipment running up to speds of 64 kbps and is current as of 2006.  It's intended for secure ISDN voice telephone.


Elcromux is trunk encryption equipment running up to speeds of 2048 kbps

In general, TROL (Tapeless Rotorless OnLine) type equipment was generally given a system name. The Elcro family, though being TROL equipment, was an exception to this rule. It was referred to as ELCROTEL, ELCROVOX and so on.


1) Henrik Teller <henrik_teller(at)vip.cybercity.dk>
2) "Bjarne Carlsen" <bca(at)fakse-ldp.dk>
3) Rohde & Schwarz.  http://www.rohde-schwarz.com/WWW/Publicat.nsf/article/n165_keyposition/$file/165_keyposition.pdf

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July 09/09