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Tactical digital communication network

ZODIAC was the name of an integrated communication system that was used by the Dutch Armed Forces from 1979 until the early 2000s. ZODIAC is an acronym for Zone Digitaal Automatisch Cryptografisch beveiligd (Area Digital Automatic Cryptographically secured). ZODIAC marked the beginning of the digital era for the Dutch Army, as all telephone and telegraphic traffic (telex) was digitised, bundled (multiplexed), automated and secured with proprietary encryption algorithms.

ZODIAC was based on the DELTACS [4] tactical area communications system, which was a joint development of Hollanse Signaalapparaten (HSA) in Huizen (Netherlands) and GTE Government Systems Corporation in Massachusetts (USA). All crypto-equipment was developed by HSA's sister company Philips Usfa (later: Philips Crypto).

The project started in 1975 and was completed in 1987. The last units were delivered in 1991. High-end digital cryptographic solutions – all developed by the Dutch manufacturer Philips Usfa – allowed greater security for an increased number of users. ZODIAC was designed to be (partly) interoperable with the communications equipment of other NATO countries (see below).

The image above shows a Dutch Army communication shelter with a fully automatied DELTACS switch, or exchange, being operated by two men. The interfaces and controls are on the left, whilst the computer is mounted in the 19" rack at the right. The image was taken from the June 1984 issue of Philips Telecommunication Review, which is available for download below [4].

In the early 2000s, ZODIAC was gradually phased out and replaced by the newer TITAAN system. To smoothen the transition, some ZODIAC components were retained during the first stages of the TITAAN implementation, such as the BVO-M (MUCOLEX II) for which external contractor TNO developed a new interface [5]. The last ZODIAC components were decommissioned in 2007.

ZODIAC equipment on this website
Bulk Encryption Device (proprietary)
Bulk Encryption Device (compatible with KG-81 - TED)
Digitaal Beveiligde Telefoon (digitally secured telephone) Spendex 50
Bulk Encryption Device (proprietary)
Digital line multiplexer
In the early 1970s, the Dutch Army started looking for a new communication system that would replace the ageing manual telephone exchanges. As most European countries were developing their own communications networks at that time, the so-called EUROCOM group was established. The aim was to establish a set of common parameters — the EUROCOM standards — that would allow the various NATO countries to communicate with each other [1][2][4].

Around 1975, the ZODIAC project was born. It was the Dutch contribution to develop a complete automated secure communication system for use by their national forces. Philips daughter HSA (now Thales) won the initial NLG 200 million contract to start development of a suitable system.

As HSA was part of the multinational Philips organization, they commissioned sister companies Philips Telecommunicatie Industrie (PTI) to carry out a system study in 1978/79, whilst Philips Usfa studied the cryptographic implications. In 1980/81, this resulted in development orders for Philips Usfa, for the design of BVO-M, BVO-T and the crypto heart of the DBT crypto phone.

A few years later, the first machines were delivered, and in 1987 the ZODIAC system was completed — 12 years after its inception. Development of ZODIAC took place in five stages:

  1. Digital
    In the first stage, the existing network was completely digitised. All digitised signals were 'stacked' or 'bundled' in a single data stream, so that they could be encrypted together. From the user's perspective, it was a fully transparent system that offered a high level of security. The first experiments were carried out in 1979 when the various stages of the Delta Modulation (CVSD) equipment were tested.

  2. Telex
    In the second stage, all teletype traffic (telex) was automated. the manually operated telex networks were replaced by ATS - Automatisch Telegrafie Systeem (Automated Telegraphy System). ATS was introduced in 1980. After this, developments slowed down somewhat. Despite the new network, it still took too long to connect a subscriber to another party and parts of the network were sometimes unavailable for too long.

  3. Automatic Telephone Exchange
    In the 3rd stage, the manually operated telephone exchange was replaced by a fully automatic switch. This allowed users to initiate a call or send data themselves, whithout the need for operator intervention.

  4. Additional nodes
    In this stage, the number of nodes in the network, was increased drastically. As the introduction of the new automatic exchanges was delayed several times, it was decided to combine stages 3 and 4, and roll them out together.

  5. New equipment
    At the same time, new equipment was introduced, such as a secure digital telephone set which became known as DBT, and a PC-based Telex system called PCT. In 1987, ZODIAC was complete, after it had passed all tests with flying colours.
ZODIAC can be connected to and is (partly) interoperable with a variety of other systems and communication standards, including the following:

  • RITA
  • Ptarmigan
  • Tri-Tac
  • NATO Alternate Mobile Way HQ

2Mb/s digital unit for the encryption and decryption of multiplexed bundled data streams. Officially designated UA-8244 or MUCOLEX II and backward compatible with the existing 1Mb MUCOLEX I units of the Royal Dutch Army.

 More information


2Mb/s digital unit for the encryption and decryption of multiplexed bundled data streams. Officially designated UA-8245 or MUCOLEX III and compatible with the KG-81 — the standard Trunk Encryption Device (TED) of the US Army.

Intended for interoperability between ZODIAC and the radio systems of other NATO partners.

 More information


Advanced ruggedized wide-band digital crypto phone, designated UA-8246 or Spendex-50, developed by Philips Usfa. It uses CVSD (delta modulation), and allows secure speech and data to be transferred at 16 kb/s or 32 kb/s.

Speech (and data) is secured by means of the secret SAVILLE cryptographic algorithm.

 More information


Personal Computer Telex (PCT) is a PC-based replacement of the older electro-mechanical teletype units (telex), consisting of a robust portable PC (slightly larger than a laptop) running DOS and suitable software.

PCT was based on the Toshiba T-3200SX portable PC, with a complementary needle-based impact printer.

Ruggedised unit for encryption and decryption of multiplexed bundled data streams at 1 mb/s. Officially designated UA-8451 or MUCOLEX I.

The device was designed and delivered during the 1970s and was already in widespread use when ZODIAC came into service.

 More information


DELTAMUX was a European standard (EUROCOM) that allowed digital switches from different countries/manufacturers to talk to each other.

Each DELTAMUX unit allows 16, 32 or 64 subscriber lines of 16 or 32 kbit/s each, to be multiplexed into a 256, 512 or 1024 kbit/s bit-stream. Mobile DELTAMUX units were suitable for the integration into communication vehicles.

 More information


In 1993, the Dutch Ministry of Defense was in desperate need for new personnel. As part of a nation-wide campaign they aired a series of five different commercials on TV. The video below is the forth in this series. It shows brief glimpses of a ZODIAC communication shelter in operation.

Places to visit
The Royal Dutch Signals Museum (Museum Verbindingsdienst) has a complete and operational ZODIAC system that can be demonstrated to the public. It was rebuilt from the contents of a former communications shelter, and consists of a complete HSA digital switch with delta-modulation (DELTAMUX), a series of Philips BVO units, some DBT phones and PCT telex units.

The images below were taken at the Royal Dutch Signals museum in July 2008, shortly before the museum was moved to its present location in Amersfoort. It is currently being shown and demonstrated in a much better environment.

At the right is the heart of the 68000-based digital switch. Note that the Crypto Ignition Key (CIK) is missing from the DBT unit in image #5, but that it is present on the DBT phones mounted inside the shelter, visible in images #1 and #2. Secure communication was only possible when the CIK was present on the DBT.

The shelter was connected to the rest of the world through a variety of mediums, including land-lines and radio links. Also in the museum is (was) a complete communication truck with DELTAMUX units, line interfaces, radio trunks, etc. Check the rightmost three images below.

Frontal view of a ZODIAC automatic digital exchange
Perspective view of a ZODIAC automatic digital exchange
Close-up of a BVO-M unit (Stream Cipher)
A typical PCT (Personal Computer Telex) unit
Close-up of a DBT
A complete vehicle-mounted Mucolex system
Close-up of the Mucolex chipher machine
The Line-unit of a Mucolex system
1 / 8
Frontal view of a ZODIAC automatic digital exchange
2 / 8
Perspective view of a ZODIAC automatic digital exchange
3 / 8
Close-up of a BVO-M unit (Stream Cipher)
4 / 8
A typical PCT (Personal Computer Telex) unit
5 / 8
Close-up of a DBT
6 / 8
A complete vehicle-mounted Mucolex system
7 / 8
Close-up of the Mucolex chipher machine
8 / 8
The Line-unit of a Mucolex system

HSA   Hollandse Signaal Apparaten
Former Philips subsidary, specializing in the development and production of equipment for the Department of Defense (DoD). Later sold to Thales.
PTI   Philips Telecommunicatie Industrie
Philips subsidary based in Hilversum (Netherlands), specializing in telecommunication solutions and automated switches.
TED   Trunk Encryption Device
American KG-81 cipher device for muliplexed digital data streams, used as a common standard between NATO countries.
  1. Bart Omloo, Afscheid van ZODIAC
    Intercom, 2004, Volume 2, p. 36-37 (Dutch)

  2. G.J. Huisman, De geboorte van ZODIAC
    Intercom, 2009, Volume 4, p. 53-55 (Dutch)

  3. Jane's Military Communications, DELTACS, ZODIAC
    Fifteenth Edition, 1994-95, p. 803.
    ISBN: 0-7106-1163-3

  4. AJW van Daal & P van der Vlist, DELTACS - a versatile tactical communication system
    Philips Telecommunicatie Industrie BV (PTI), Hilversum (Netherlands), 1984.
    Reprint from Philips Telecommunication Review, Vol. 42, No. 2, pages 74-89.

  5. A. Regtien & HW Evers,
    TITAAN: Flexibel en veelzijdig, maar ook veilig en betrouwbaar

    Intercom, 2001, Volume 4, p. 58-59 (Dutch)

  6. Koninklijke Landmacht, ZODIAC (Dutch)
    Published by the Human Resource Department of the Dutch Army. 1988.
    Crypto Museum #301329.

  7. Holland Signaal, DELTACS Leaflet
    Delta-modulation Tactical Area Communications System (English). 1987.

  8. MJ van de Fliert, PTT op Wielen, verbindingen altijd 'op scherp'
    Description of ZODIAC in action (Dutch). Legerkoerier. December 1988.
Further information
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