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REVIEW 1 major objections 3 minor 77 references

Oprema -- The Relay Computer of Carl Zeiss Jena

T0 review · 1 major / 3 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read The Oprema relay computer was built in 14 months at Carl Zeiss Jena and became the first universal computer in the GDR.

desk verdict Solid archival reconstruction of the Oprema with a genuine correction and new technical detail; the abstract's 14-month timeline overstates what the body itself concedes. read the letter →

arxiv 1908.09549 v1 pith:PAWJHFIV submitted 2019-08-26 cs.GL

Juergen F. H. Winkler This is my paper · ORCID
classification cs.GL
keywords OpremarelaycomputerCarlZeissJenahistoryofcomputingGDRplugboardprogramstoragefloating-pointarithmeticWilhelmKämmerer
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Oprema was a relay computer for optical calculations, initiated by Herbert Kortum and designed and built under Wilhelm Kämmerer at Carl Zeiss Jena. The paper tries to establish that the two identical machines were designed and built in roughly 14 months, from early April 1954 to mid-1955, with formal completion reported on 30 December 1954, and that this made the Oprema the seventh universal computer in Germany and the first in the GDR. It reconstructs the machine from a surviving work diary and scattered technical notes: 8,313 relays per machine, plugboard program and data storage, a four-address 27-bit instruction format, and decimal floating-point arithmetic with special values for zero, infinity, and indeterminate results. If these claims are right, the GDR's computing history begins in 1954 with a relay computer built by an optics company under tight political deadlines, not in the later decade with transistor machines.

What carries the argument

The load-bearing source is Gerhard Lenski's handwritten work diary, 58 pages covering 5 April to 24 December 1954, which fixes the project's start, its weekly decisions, and the final completion push; its attribution to Lenski rests on handwriting, his role as head of physical design, and the testimony of a later team member. The second load-bearing document is Kortum's May 1958 report, which explicitly denies that any concrete Oprema design work was done while he and Kämmerer were detained in the Soviet Union; without that denial the designed-and-built-in-1954 claim loses its force. On the technical side, the central mechanism is the 3-phase pulse system with cam-operated contactors, which switches relay contacts only when no current flows, and the control sequences ('Führungsketten') that propagate an activation wave through chains of bistable latching relays to sequence instruction execution.

What would settle it

Finding a dated Oprema design document, such as a wiring diagram, an instruction-format sketch, or a relay count, from before 5 April 1954 in any surviving collection of the participants' papers would refute the claim that the design work began in Jena in 1954.

Watch

Extended reading notes

Core claim

The central claim is that the Oprema was a genuine program-controlled relay computer, built as two identical machines, and that its design and construction were completed within roughly fourteen months. Each machine held 8,313 relays, about 45,000 selenium rectifiers, 250 km of wire, and an estimated 500,000 solder joints; programs of up to 300 instructions were wired onto plugboards, and data lived in plugboard constants, cyclic memories, and 32 relay registers. The instruction format was four-address and 27 bits long, and the number format was normalized decimal floating point in excess-3 BCD, with a 39th bit encoding zero, infinity, and indeterminate values, features that put the Oprema in the same family as Zuse's special-value floating point and, later, IEEE 754. The reconstruction is anchored by Lenski's work diary, which shows design work beginning on 5 April 1954, by the 17 May 1954 ministry meeting at which Kortum promised completion by the end of 1954, and by Kortum's May 1958 report denying that concrete plans were smuggled out of the Soviet Union. The paper concludes that the Oprema was the seventh universal computer in Germany, after the Z3, Z4, G1, Z5, ALWAC, and G2, and the first in the GDR.

Load-bearing premise

The 14-month timeline rests on Kortum's May 1958 statement that he and Kämmerer did no concrete Oprema design work in the Soviet Union, and on the attribution of the anonymous work diary to Gerhard Lenski as a complete daily record.

Editorial extensions

If this is right

  • Programs of up to 300 instructions were wired into plugboards, yet the machine could still execute conditional and unconditional jumps and loops; Oprema was program-controlled without using an electronic stored program.
  • The planned twin-machine checking mode, two machines running the same program and comparing results after each instruction, was never wired up because both machines worked reliably after debugging; the Oprema therefore always ran as two separate computers.
  • Productive use rose from 64% of possible hours in 1956 to 88% in the first half of 1960, which supports the paper's picture of a relay machine that, once debugged, was dependable enough for production computing.
  • At Carl Zeiss Jena, the share of lens-design samples that reached production rose from 7% in 1954 to 83% in 1957, a change the paper ties to the Oprema's ability to trace more rays and handle aspheric surfaces.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • A simulation of the Oprema's instruction set and cyclic-memory mechanism would let a modern reader measure how much of the 1955–1957 productivity jump came from the machine itself rather than from the team's growing experience; this test is not in the paper.
  • The paper's rounding analysis suggests a hardware trick, roundNorm, which avoids the ripple-overflow adder needed by roundTiesToEven and could be worth revisiting in low-power designs where a full adder is expensive; this is an engineering consequence the paper does not draw.
  • The Oprema's cyclic memories, which feed successive values through registers with jump sockets, can be read as an index-register mechanism shaped by ray-tracing workloads; a comparative study of early index mechanisms across relay and tube machines would place it in a broader lineage.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

1 major / 3 minor

Summary. This paper is an archival history of the Oprema (Optikrechenmaschine), a relay computer developed at Carl Zeiss Jena (CZJ) in 1954–1955 under Wilhelm Kämmerer's technical leadership and Herbert Kortum's managerial sponsorship. The paper claims that the Oprema was the seventh universal computer in Germany and the first in the GDR; that it consisted of two identical machines, each containing 8,313 relays, roughly 45,000 selenium rectifiers and about 250 km of cable; and that machine-1 was designed and built in about 14 months, measured from the first entry of Gerhard Lenski's work diary (5 April 1954) to its ready-for-use date around mid-June 1955. It reconstructs the machine's plugboard-based program storage, its four-address 27-bit instruction format, its decimal floating-point arithmetic with special values for zero, infinity and indeterminate, and its arithmetic algorithms, including a distinctive rounding scheme. It also recounts the biographies of Kämmerer and Kortum, their work in the KoKor development lab, their seven years of detention in the Soviet Union, the approval of the project by minister Rau in May 1954, the machine's operational record from 1955 to 1963, and the historiographical debate over whether Kortum should count as a German computer pioneer.

Significance. If the reconstruction holds, the paper secures the Oprema's place in the chronology of German and GDR computing and provides the most detailed technical account of the machine available, while correcting at least one figure in the secondary literature (Cortada's 25,000-relay count for the two machines combined). The paper's main strength is its archival grounding: the central claims are anchored in specific primary sources, including Lenski's work diary, memos in the CZJ and Deutsches Museum archives, Kortum's May 1958 report, and Kämmerer's 1955–1960 technical publications. The author consistently flags attribution inferences, contradictions between sources, missing documents, and gaps in the technical record: the attribution of the anonymous work diary to Lenski is argued step by step; the tension between Helga Kämmerer's recollection of Oprema discussions on Gorodomlia and Kortum's 1958 denial is reported frankly; and the incompleteness of the anonymous arithmetic notes, and the contradiction in the rounding description in Kämmerer's 1960 book, are stated rather than concealed.

major comments (1)
  1. [Abstract; §Design and Construction of the Oprema] The abstract's headline timing claim is not fully supported by the paper's own body text. The abstract says that 'basic experiments, design and construction of machine-1 were all done, partly concurrently, in the remarkably short time of about 14 months,' without qualification. In the Design and Construction section, however, the author states that 'Kämmerer had already done some significant design work before April 1954, especially after his return to Jena on 21 November 1953' (supported by endnote 31), and the same section later concedes that 'there is no clear-cut method to determine such time periods.' The 14 1/3-month figure is computed from the first Lenski work-diary entry (5 April 1954) to mid-June 1955, and the text also records the alternative start date of 17 May 1954 (minister Rau's approval). The stress-test concern therefore lands in part: the abstract overstates what the body's own evidence supports, and the inconsistency is internal. The fix is local: the abstract should specify the interval being measured (e.g., 'from the start of the documented design-and-construction work in April 1954') and should acknowledge the earlier design work discussed in the body. The body's own discussion is already appropriately hedged and does not require substantive change.
minor comments (3)
  1. [§Operation and Use] The sentence 'During these weeks the machine was operated 13286 hours per week' contains a garbled figure; endnote 86 shows the intended comparison is between 136, 1360 and 1320 hours, so the main text should read approximately '132 hours per week' (or state the 1320-hour ten-week total) and the endnote should be reconciled with the corrected wording.
  2. [§Technical Properties, Reliability subsection] The isolated phrase 'on average almost 10 % unnoticed errors' appears as a dangling fragment immediately before Table 2; it should either be integrated into the preceding paragraph about Kämmerer's human-versus-machine experiment or deleted.
  3. [Throughout] Several typos and typesetting artifacts should be cleaned up: 'a relay computer were electromechanical relays' should be 'where'; 'the Havard Computation Laboratory' should be 'Harvard'; 'German Metereological Service' should be 'Meteorological'; 'who's now head of his own company' should be 'whose'; 'Seminumerical Algoritms' (endnote 30) should be 'Algorithms'; and 'GoldsƟne' (endnote 28) should be 'Goldstine' to match the spelling used elsewhere.

Circularity Check

0 steps flagged · score 2.0 of 10

No circular derivation: the paper is a historical reconstruction, and its two self-citations are not load-bearing.

full rationale

The paper makes no formal derivation, no numerical fit, and no prediction that could reduce by construction to an input. Its central claims about the Oprema's design, timeline, relay count, ranking as the seventh universal computer in Germany, and first computer in the GDR are grounded in primary archival sources: Lenski's work diary (UACZ, BACZ 27995), Kortum's May 1958 report, Kämmerer's reports, Zeiss archive materials, and contemporary records. The author cites two of his own earlier publications, in endnotes 33 and 93, but these support only peripheral details: the failed search for evidence that Bertele used Zuse's Z4, and a comparison of Z5 versus Oprema speeds. Neither is the basis for the paper's headline claims. The 14-month figure is presented as a rough estimate, and the paper explicitly acknowledges the ambiguity: 'there is no clear-cut method to determine such time periods' and notes that Kämmerer had done significant design work before April 1954. That is historical uncertainty, not circularity. No uniqueness theorem is imported, no ansatz is smuggled in via citation, and no known result is merely renamed. The analysis therefore finds no significant circularity; at most there are two minor self-citations that do not carry the central narrative.

Assumptions & free parameters 0 free parameters · 3 assumptions · 0 invented entities

No fitted parameters or invented entities are present. The historical claims rest on archival sources and retrospective accounts; the main assumptions are source authenticity, the truthfulness of Kortum's denial of Soviet-era design work, and the fidelity of later technical descriptions of the arithmetic.

assumptions (3)
  • domain assumption The cited archival documents, including the Lenski work diary, Kortum report, Schumann memos, and anonymous technical notes, are authentic and accurately transcribed.
    The chronology, design decisions, and technical reconstruction are built on these primary sources; the author provides quotes and archive signatures but not scans.
  • domain assumption Kortum's May 1958 statement that no concrete Oprema design work was done in the Soviet Union is truthful.
    This assumption underpins the 'designed and built in 1954' claim; the paper reports a conflicting family memory that K&K discussed Oprema ideas while detained.
  • domain assumption Kämmerer's 1960 book and the anonymous notes accurately describe the implemented arithmetic except where the paper identifies contradictions.
    The machine was dismantled in 1963 and the technical documentation is incomplete, so the arithmetic reconstruction necessarily relies on these later descriptions.

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Cite this review

Pith. "Pith review of Oprema -- The Relay Computer of Carl Zeiss Jena." pith.science (2026). https://pith.science/paper/PAWJHFIV

@misc{pith2026190809549,
  author       = {Pith},
  title        = {Pith review of: Oprema -- The Relay Computer of Carl Zeiss Jena},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/PAWJHFIV}},
  note         = {Machine review of arXiv:1908.09549}
}
read the original abstract

The Oprema (Optikrechenmaschine = computer for optical calculations) was a relay computer whose development was initiated by Herbert Kortum and which was designed and built by a team under the leadership of Wilhelm Kaemmerer at Carl Zeiss Jena (CZJ) in 1954 and 1955. Basic experiments, design and construction of machine-1 were all done, partly concurrently, in the remarkably short time of about 14 months. Shortly after the electronic G 2 of Heinz Billing in Goettingen it was the 7th universal computer in Germany and the 1st in the GDR. The Oprema consisted of two identical machines. One machine consisted of about 8,300 relays, 45,000 selenium rectifiers and 250 km cable. The main reason for the construction of the Oprema was the computational needs of CZJ, which was the leading company for optics and precision mechanics in the GDR. During its lifetime (1955-1963) the Oprema was applied by CZJ and a number of other institutes and companies in the GDR. The paper presents new details of the Oprema project and of the arithmetic operations implemented in the Oprema. Additionally, it covers briefly the lives of the two protagonists, W. Kaemmerer and H. Kortum, and draws some comparisons with other early projects, namely Colossus, ASCC/Mark 1 and ENIAC. Finally, it discusses the question, whether Kortum is a German computer pioneer.

Figures

Figures reproduced from arXiv: 1908.09549 by the authors.

Figure 1
Figure 1. Wilhelm Kämmerer. Courtesy of Helga Kämmerer [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 4
Figure 4. One of the Oprema Machines. Source: ZEISS Archiv [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. People working inside Oprema on 15 Dec. 1954. [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗
Figures from the paper (9 more)
Figure 6
Figure 6. Figure 6: Block Diagram of the Oprema. (drawn by the author) [PITH_FULL_IMAGE:figures/full_fig_p010_6.png]
Figure 8
Figure 8. Figure 8: Relay states and direction of current. Part of [PITH_FULL_IMAGE:figures/full_fig_p010_8.png]
Figure 9
Figure 9. Figure 9: The 3−Phase Pulse System of the Oprema [PITH_FULL_IMAGE:figures/full_fig_p010_9.png]
Figure 10
Figure 10. Figure 10: Basic principle of the control se￾quences. The activation wave has reached relay n+1 (drawn by the author) [PITH_FULL_IMAGE:figures/full_fig_p011_10.png]
Figure 11
Figure 11. Figure 11: The Control Sequences of the Oprema. Fig. 78 from [PITH_FULL_IMAGE:figures/full_fig_p012_11.png]
Figure 14
Figure 14. Figure 14: The four cyclic memories (drawn by the author). Y0 Arithmetic Unit Y1 Y2 Y3 Register Register Register Register [PITH_FULL_IMAGE:figures/full_fig_p017_14.png]
Figure 15
Figure 15. Figure 15: A cyclic memory with two jumps (drawn by the [PITH_FULL_IMAGE:figures/full_fig_p018_15.png]
Figure 17
Figure 17. Figure 17: The Retrofocus Wide-Angle Lens Flektogon 4/50 with [PITH_FULL_IMAGE:figures/full_fig_p018_17.png]
Figure 18
Figure 18. Figure 18: Kämmerer (3rd from right) receives the Konrad Zuse Medal; Zuse second from right. Courtesy of GI Bonn [PITH_FULL_IMAGE:figures/full_fig_p023_18.png]

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Reference graph

Works this paper leans on

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Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.