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Electronic digital building blocks

Gretag-Bausteinsystem (Gretag Building Block System), was a series of pre-assembled digital building blocks, developed in the early 1960s by Gretag AG in Regensdorf (Switzerland). These electronic circuit blocks are commonly seen as the forerunners of the Integrated Circuit (IC), and are similar to the Circuit Blocks made by Philips, and the FLYBALL modules made by the NSA.

The image on the right shows examples of the Gretag building blocks, as they were printed on the cover of a folder with datasheets, probably from the early 1970s [A]. They were available for different speeds, known as 10, 20 and 30 series.

A patent for their construction was filed in 1964 in Canada, by Kurt Ehrat and Dieter Eckstein on behalf of Gretag AG. It was issued in June 1967, with a priority date of 5 December 1963. Never­theless it is unlikely that their claim would have held if tried in court, as both Philips and the NSA already had them on the market for some years.
Gretag building blocks

In such case, the claim would have been declared invalid due to prior art. The construction of Gretag's blocks is very similar to the NSA's FLYBALL modules, although this may not have been known to Gretag at the time, as they were used in (secret) military equipment. As far as we know, the NSA never patented the FLYBALL modules, but a patent for a similar construction — which is also known as a cordwood construction — was filed in the US in 1960 by Vito Elarde [3].

The Gretag digital building blocks were first used in the earliest design of the TC-534 — Gretag's first fully electronic cipher machine — developed for use by the Swiss Army. The image on the right shows one of its circuit boards, which holds no less than 18 of these blocks.

In order to generate some return on investment, Gretag decided to make this technology available to other manufacturers — as OEM parts — but it remains to be seen whether this was a success, as other parties had better distribution means.
One of the circuit board of the TC-534, with 18 digital building blocks

Companies like Philips already had similar products on the market for several years and were making the move to the new Integrated Circuits (ICs) — based on TTL technology — that had just become available. The TC-534 encryptor was later redesigned with TTL technology as well [1].

Gretag building blocks
Gretag building block
1 / 3
Gretag building blocks
2 / 3
Gretag building block
3 / 3
3 / 3

  • 10
    50 kHz
  • 20
    100 kHz
  • 30
    1 MHz
Known types
  • DC-10
    Decimal Counter
  • FF-20
  • PAG-24
    Dynamic Quad AND gate
  • NOR-I-25
    5-input NOR gate with inverted output
  • RD-20
    Reset Impulse Driver
  • PD-20
    Impulse Driver
  • 2/NOR-23
    Dual 3-input NOR gate
  1. Collection of datasheets of above listed blocks
    Date unknown, but estimated mid-1970.

  2. Canadian Patent 760,652, Method and jig for assembling ... module
    Filed 2 December 1964 by Kurt Ehrat and Dieter Eckstein on behalf of Gretag AG.
    Issued 13 June 1967. Priority 5 December 1963.

  3. Vito D. Elarde, US Patent 3151278
    Filed 22 August 1960. Issued 29 September 1964.
  1. Gerhard Sulger Buel, Documentation and background information
    Personal correspondence, June 2013.

  2. Gretag, Advert for Gretag-Bausteinsystem
    14 September 1965.
Further information
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Crypto Museum. Created: Sunday 31 March 2019. Last changed: Thursday, 27 February 2020 - 23:36 CET.
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