US 2762913

I'll search for the specific patent number and any related 2026 litigation.

Search results for US Patent 2,762,913

Important number-collision note (do not conflate): Searches for "2762913" also return unrelated documents sharing the digits — EP 2762913 ("Highly integrated circuit architecture," ViaSat Inc., appl. 14163942.7) and RU 2762913 C1 (Russian arthroscopy-training patent, Botkin Hospital, Moscow). These are different patent families in different jurisdictions, not the US patent. Per the strict instruction, I am flagging them rather than merging them. The authoritative record for the ID you asked about is US 2,762,913 A.

Bibliographic summary (US 2,762,913 A)

Abstract

There is no abstract. US 2,762,913 was filed June 13, 1955 — before the January 1, 1957 cutoff after which US applications were required to include an abstract. The Google Patents "Definitions" block is machine-extracted summary text, not an official abstract. The closest official summary is the "Objects of the invention" passage in the specification (e.g., providing a warning system in which each end of each vehicle carries a transmitter radiating an identifiable signal ahead/behind and a receiver picking up such signals from other vehicles, with all equipment self-contained on the vehicles).

First-claim / independent-claim overview

The patent has four independent claims: 1, 3, 7, and 8 (claims 2, 4–6, 9–10 depend from them).

• Claim 1 — System-level combination. Multiple transmitters all tuned to the same frequency; one mounted at the front and one at the rear of each vehicle, with front units radiating ahead and rear units radiating behind. Front transmitters have coding means producing a "first pulsed signal"; rear transmitters produce a "second pulsed signal." Receivers tuned to that frequency sit adjacent each transmitter and are directional (front receivers see only ahead; rear receivers only behind). Control means disable each receiver while its adjacent transmitter is radiating. The key twist: each signal's pulse repetition rate is chosen so it can be picked up by a receiver sitting next to a transmitter radiating the other signal — i.e., cross-pickup between opposite-end units is deliberately preserved.

• Claim 3 — Transmit/receive unit (the building block). A unit with a unidirectional antenna; a transmitter power-feeding it; coding means able to produce either a first or second pulsed signal; selector means choosing which is produced; a receiver coupled to the same antenna; and a control means between antenna/transmitter/receiver that blocks energy from reaching the receiver while the transmitter fires. Signals are characterized such that while this unit radiates one signal and a similar unit radiates the other, the receiver can still pick up the other signal.

• Claim 7 — Front/rear transmitting-and-receiving combination. Front transmitting means radiate forward pulses at a fixed frequency and a "first rate"; rear transmitting means radiate backward at the same frequency and a "second rate." Receiving means are mounted at front and rear, with directional pickup. Means disable a receiver when the same-end transmitter on the same vehicle is radiating. The first and second rates are related so that a front receiver can pick up a rear transmitter (and vice versa) while the local same-end transmitter is operating.

• Claim 8 — Multi-unit / generator-level combination. A first plurality of front-end transmit-receive units (each antenna directing pulses ahead, each with a coupler blocking reception during transmission) and a second plurality of rear-end units (same, directed behind). Each unit is driven by its own pulse generator producing continuous pulse trains at a "particular" rate. The rate spacing is asymmetric: every rear generator differs from every front generator by substantially more than the rear generators differ from each other — and, in the literal claim language, every front generator likewise differs from every rear generator by substantially more than the front generators differ among themselves. Claim 9 adds reproducing means that distinguish front-origin from rear-origin pulses; claim 10 adds aural and visual indication.

Drafting caveat on claim 8: the final two clauses are largely duplicative/reciprocal as printed, and the Google Patents OCR of this claim is visibly incomplete/garbled. My plain-language reading above is based on the text as provided; treat the exact rate-spacing wording as requiring verification against the printed patent PDF rather than as authoritative.

What the specification adds (context for the claims)

• Preferred pulse coding: two distinctly different repetition rates, e.g. 200 pulses/sec vs. 2,000 pulses/sec, one for front, one for rear.
• Anti-"synchronized blocking": free-running unstabilized multivibrators so each front transmitter drifts slightly off the nominal rate, preventing two same-end units from locking each other out while their local receivers are blanked.
• Microwave band preferred; antenna beam ≈20° horizontal, 5–10° vertical; rotatable in azimuth; range ≈5 miles (just beyond sight/sound).
• Duplexer/TR cell as the transmit-receive isolator; a third "emergency/standing" signal made by toggling front↔rear at ≤1–2 Hz, selectable via a three-position switch; axle-driven selector for direction of travel.
• A built-in tester: capacitive pick-off of transmitter output, level-set by adjustable resistor, periodically injected past the duplexer into the receiver input by a relay/timer — a self-test feature claimed in dependent claim 6.

CAFC 2026 dockets / litigation

No CAFC 2026 docket involving US 2,762,913 was found. That is expected: the patent expired September 11, 1973, roughly 53 years before the current date, so it is not assertable and cannot be the subject of a live appeal. My searches surfaced 2026 Federal Circuit activity (e.g., Contour IP Holding LLC v. GoPro, Inc., Fed. Cir. No. 2026‑2012), but none of it concerns this patent. The only "Metrom Rail" 2026‑era material in the results relates to other patents (e.g., IPRs on the Grisham/Nixon family), and US 2,762,913 appears there purely as a citation in those patents' reference lists.

Uncertainty statement

• Bibliographic data, claims text, and the expiration status come from the Google Patents full-text record you supplied and are corroborated by the uspto.report entry (issue date 1956‑09‑11) and by Justia's citation listing ("2762913 | September 1956 | Jepson"). I treat these as authoritative.
• I could not independently confirm that a formal abstract exists — as explained, none should, given the 1955 filing date.
• I did not verify the printed claim 8 wording against the original patent PDF; the OCR of that claim is clearly defective, and I flag that explicitly rather than reconstructing it silently.
• If you need litigation-free confirmation, the definitive check is the USPTO PatentCenter/Assignment records and the Federal Circuit docket (PACER/CM‑ECF) searched by patent number, which I cannot query directly here.

I'll search for litigation records involving US patent 2762913.

Let me search more targeted litigation databases.

Let me check the litigation-specific databases directly.

Search Results: Litigation Involving US Patent 2,762,913

No litigation is known involving US Patent 2,762,913.

I searched litigation-focused sources (Unified Patents litigation portal, Docket Alarm, CourtListener, and general web queries for the patent number in a litigation context). No PTAB proceeding, district court case, ITC action, or CAFC appeal was identified in which US 2,762,913 was asserted, challenged, or otherwise at issue.

Why this is unsurprising

• The patent is long expired. Per the Google Patents record, US 2,762,913 issued 1956-09-11 (filed 1955-06-13) and had an anticipated expiration of 1973-09-11, with legal status "Expired – Lifetime." Any infringement suit would have had to be filed within the ~17-year term, and none appears.
• No prior art cited on its face. The granted patent states "No references cited," indicating it issued as an early, unexamined in this respect, low-profile grant.
• Narrow, single-inventor ownership. Inventor William L. Jepson (Los Angeles), assignee listed as "Individual." There is no corporate owner chain (e.g., no Westinghouse Air Brake or major railroad assignee) that would typically generate enforcement activity.

Important caveat on the number "2762913"

The number 2762913 appears in several unrelated records, and I have deliberately not conflated them with US 2,762,913:

• RU2762913C1 – a Russian patent (ГБУЗ ГКБ им. С.П. Боткина, filed 2020, granted 2021) on a knee-arthroscopy triangulation training method. Different jurisdiction, different subject matter.
• EP2762913 – a European patent (ViaSat Inc.) titled "Highly integrated circuit architecture," grant published 2018-11-21. Different jurisdiction, different subject matter.
• The number also appears incidentally in unrelated municipal and corporate documents.

None of these is US Patent 2,762,913, and my search found no litigation for any of them either, but they are outside the scope of your request.

Note on the search process

• Unified Patents' portal and Docket Alarm surfaced only a patentability search-string reference to "2762913" inside an unrelated 2019 IPR exhibit (Westinghouse Air Brake Technologies, IPR2026-00134, Exhibit 1002) — this is a prior-art search log citation, not litigation involving the patent.
• The "Cited By" lists on the patent page (Metrom Rail, Harsco, Westinghouse, etc.) reflect later patents that cite US 2,762,913 as prior art, which is not the same as litigation over the patent itself.

If you have a specific district, court docket, or party in mind, providing it would let me run a narrower PACER/CourtListener query, but based on the available evidence, there is no known litigation history for US Patent 2,762,913.

I'll verify the structured "no proceedings" signal against live sources before finalizing.

Proceedings overview

Zero AIA trial proceedings have ever been filed on US 2,762,913 — 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials — which is the canonical answer from the structured "PTAB proceedings on file" block (USPTO Open Data Portal) and is corroborated by my independent searches. The defensive posture this gives a defendant is not "hardened patent" and not "troll with dead claims"; it is closer to "non-justiciable antique." No PTAB panel has ever construed a claim of this patent, no petitioner has ever been estopped, and no claim of claims 1–10 has ever been canceled or confirmed in an AIA forum. The reason is chronological, not tactical: this patent is a pre-AIA, 1955-filing, expired-since-1973-09-11 document.

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For each proceeding

There are none. Rather than fabricate proceeding numbers, the useful work here is (a) explaining why none can or would exist, and (b) isolating the false positives that a careless records check will surface.

Why AIA trials are structurally unavailable

Bottom line: the only AIA track that could ever have been invoked is IPR, and no one has ever invoked it. I found no ex parte reexamination record either (a non-AIA avenue that sometimes appears alongside IPRs) — so the patent's claims have never been re-examined or canceled in any post-grant forum, USPTO or otherwise. That is not an endorsement of their strength; it reflects that the enforcement window closed in 1973.

Near-misses and conflation traps (do not merge these)

These surfaced in search and each one is a different matter — flagged, not combined, consistent with the number-collision rule applied earlier in this analysis:

1. PTAB petitions 1550896, 1550912, 1550914, 1550883, 1494874 (ptacts.uspto.gov) — these are real, active AIA petitions, but they attack Metrom Rail / Grisham-family worker-protection and collision-avoidance patents (the '131, '471, '595 patents; e.g., IPR2023-00468). US 2,762,913 appears in those filings only as cited prior art in a reference table — the entry reads 2,762,913 A 9/1956 Jepson B61L 23/34 246/124. It is a citation, not a challenged patent.
   • https://ptacts.uspto.gov/ptacts/public-informations/petitions/1550912/download-documents (FWD text discussing claims 8, 9, 17, 19 of the '131 patent — not claims of 2,762,913)
2. IPR2026-00134, Westinghouse Air Brake Technologies Corp. — a 2026 IPR on RE47,835. Exhibit 1002 (a file history) contains a patentability search string listing ("2762913" | "5554982" | "5620155").PN. That is a search-log artifact, not a proceeding number for this patent.
   • https://www.docketalarm.com/cases/PTAB/IPR2026-00134/Westinghouse_Air_Brake_Technologies_Corporation/
3. EP 2762913 ("Highly integrated circuit architecture," ViaSat Inc., appl. 14163942.7, granted 2018-11-21) and RU 2762913 C1 (Botkin Hospital, Moscow arthroscopy-training method, priority 2020-11-19) — unrelated families sharing the digits, as flagged in the earlier section. Neither is PTAB-eligible matter.

Correction to the earlier-generated section

The prior summary flagged a "drafting caveat" suggesting the closing clauses of claim 8 might be an OCR artifact. On re-reading the authoritative full text supplied in this prompt, both reciprocal clauses are present and complete: "…each varying in pulse rate from any of said first generators by substantially more than said second generators vary from each other, and each of said first generators varying in pulse rate from any of said second generators by substantially more than said first generators vary from each other." The oddity is genuine mutual reciprocity in the original 1955 drafting, not dropped characters. I am narrowing (not reversing) that earlier caveat — the claim-8 rate-spacing language is authentic, though still redundant on its face.

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Strategic summary

Claim-status ledger. Under AIA practice there is nothing to report: claims 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 are all CANCELED: none / SUSTAINED: none / UNTESTED: all ten. No claim of US 2,762,913 has been the subject of an instituted trial, an FWD, a settlement, or an appeal. The claims remain exactly as they issued on 1956-09-11 and as they lapsed on 1973-09-11. Any assertion of these claims today fails at the threshold on expiration and laches/enforceability grounds long before a § 102/§ 103 merits fight — infringement liability under 35 U.S.C. § 271 attaches only to acts occurring during the patent term, and this term ended 1973-09-11 (see the "Anticipated expiration" entry at https://patents.google.com/patent/US2762913/en).

Estoppel landscape — there is none to speak of. Because no IPR, PGR, or CBM was ever filed, no petitioner (or privy) is subject to § 315(e)(2) estoppel, and conversely no defendant is precluded from raising any prior-art ground — § 315(e) estoppel is asymmetric and only ever constrains a petitioner who lost. Practically, the freedom is academic: an expired patent cannot be enforced, so there is no infringement action in which § 102/§ 103 grounds would need to be raised. If someone nonetheless petitions, note that a pre-AIA patent's validity is judged under pre-AIA §§ 102/103, not the AIA novelty provisions (AIA § 3(n)(1)), which affects the available art categories and the on-sale/public-use calculus.

Pattern signals. There is no pattern to detect on this patent. No repeat petitioner, no defensive aggregator (no Unified Patents or RPX filing), and no patent-owner appellate activity — unsurprising, since the "current assignee" is listed as Individual with no assignment of record, the inventor (William L. Jepson) is deceased, and the patent has been public domain since 1973. The 36–49 forward citations are downstream patents citing this disclosure as background — including Studebaker-Packard US 2,831,182, GM US 3,235,025, Burlington Northern US 5,577,469, and numerous Metrom Rail and Harsco end-of-train / worker-protection patents (https://patents.google.com/patent/US2762913/en) — which is evidence of influence on the art, not of assertion of the patent.

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Recommended next steps

1. Say it plainly: no PTAB activity exists, and none ever has. The structured ODP block returns zero AIA trials, and my searches found no ex parte reexamination, no CBM, no PGR, and no Federal Circuit appeal. The absence here is not the usual "well-asserted patent that hasn't been IPR'd yet" signal; it is the signal of a patent that expired 53 years ago and was never worth challenging.
2. Verify in the two authoritative places before relying on this in a brief. (a) USPTO PTAB E2E / PatentCenter trial search by patent number, to confirm zero proceedings; (b) USPTO Assignment records, to confirm no assignee recorded. Links: https://patents.google.com/patent/US2762913/en and https://uspto.report/patent/grant/2762913 (issue date 1956-09-11). Google Patents independently shows "Expired – Lifetime," anticipated expiration 1973-09-11, and "No references cited" during prosecution.
3. Do not conflate. If a docket search returns "2762913" inside an IPR, check whether it appears as a cited reference (as in the Metrom Rail '131 FWD and the Westinghouse RE47,835 exhibit) rather than as the challenged patent. Only the latter counts.
4. If a demand letter cites US 2,762,913, the response is not an IPR — it is a one-line invalidity/enforceability answer: the patent issued 1956-09-11 and expired 1973-09-11, so there can be no actionable infringement and no live claims to challenge. An IPR petition would be a waste of filing fees; a declaratory-judgment or § 285 motion practice is the sharper tool if a would-be plaintiff persists.

Uncertainty statement

• The zero-proceeding finding rests on the canonical structured block (USPTO ODP) plus my searches of PTAB petition portals, Docket Alarm, and Google Patents/Justia citation tables. I could not query PACER or PTAB E2E directly, so treat this as high-confidence but not a substitute for a live E2E docket print.
• I did not find any non-PTAB post-grant challenge (ex parte reexam, inter partes reexam under pre-AIA § 311, or a 1950s–70s interference) — but my sources for pre-1981 USPTO post-grant history are limited, and I state that as a gap rather than a confirmed negative.
• No judge panel, institution decision, FWD, settlement term, or appeal disposition is reported above because none exists; I have invented none. Every proceeding number in this section belongs to a different patent or is a search-string artifact, and is labeled as such.

I'll verify the assignment record before writing anything, since the authoritative record already hints there may be none.

Let me try to reach the assignment records directly and check the PatentCenter/assignment indexing.

Let me check the inventor's background and Google Patents' legal-events record for any post-issuance transfers.

Inventors

Pattern notes: This is a sole-inventor, non-corporate filing. The specification is written in first person singular ("I claim as my invention:"), the applicant-of-record is the inventor himself, and Google Patents lists both Original Assignee and Current Assignee as "Individual." There is no evidence of a corporate employer assigning or being assigned rights — and, critically, no 12-month-departure or pre-fire-sale pattern can exist here because there was never a corporate assignee to depart from. No co-inventor, no team, no employment-agreement trail.

Original assignee

There is no third-party assignee. The patent issued to the inventor personally — the "original assignee" field is the individual, William L. Jepson. Specifically:

• Entity on the issued patent: None beyond the inventor. US 2,762,913 carries no corporate assignee line; there is no "assignor: Jepson → Company" record.
• Product embodying the claims: No evidence of one. The specification frames the invention as an illustrative/proposed system ("the description merely describes a preferred embodiment … given by way of illustration or example only") and explicitly contemplates adaptation to "any transportation system," which is aspirational drafting rather than a shipped commercial product. I found no product literature, catalog, or advertising tying Jepson to a manufactured railway proximity-warning product.
• Primary line of business: Unknown / not determinable. No company is named. Given the 1955 filing date, a Los Angeles-based individual inventor working in railway signaling or RF is plausible, but that is inference, not record evidence — I flag it as unverified.
• Current status: The patent is Expired – Lifetime, anticipated expiration 1973-09-11. Any natural-person owner would be long deceased; no successor entity exists on the record to be operating, acquired, or in bankruptcy.

Contradiction check against the prior section: none. The earlier "Patent summary" already recorded assignee as "None listed — Individual," which the searches here corroborate. No correction needed.

Assignment timeline

No assignment records exist for US 2,762,913. I searched the Google Patents full-text record (whose "Legal Events" table contains only four entries: application filed 1955-06-13, priority to US 514,976, application granted 1956-09-11, and anticipated expiration 1973-09-11 — no assignment, security-agreement, merger, change-of-name, license, or release events), the uspto.report grant page, and the Justia citation listing. Nothing surfaced a reel/frame.

Per the task instruction, I am stopping this section here rather than fabricating entries.

What this means, stated plainly: A patent with zero recorded post-issuance assignments is a positive finding, not a data gap. It means the inventor retained ownership for the entire life of the patent, the patent was never securitized, never contributed to a corporate portfolio, never sold at a bankruptcy sale, and never fed into an assertion vehicle. There is no chain to reconstruct — the chain is a single node: Jepson, 1955–1973. The only theoretical gap is unrecorded ownership changes, which are legally ineffective against subsequent purchasers under 35 U.S.C. § 261 and would not appear in Assignment Center in any event.

Timeline diagram

timeline
    title Ownership of US 2762913
    1955 : Filed by William L Jepson
         : Sole inventor no corporate assignee
    1956 : Patent issued to Jepson
    1973 : Patent expired
         : No assignments ever recorded

NPE / troll-pattern signals

Verdict

Insufficient data — and, more precisely, affirmatively non-asserting.

Justification: the record contains no recorded assignments whatsoever — Google Patents' legal-events table for US 2,762,913 shows only the 1955-06-13 filing, the 1956-09-11 grant, and the 1973-09-11 anticipated expiration, with Assignee and Original Assignee both listed as "Individual." With no reel/frame entries to analyze, the enumerated NPE criteria cannot be triggered: there is no shell-entity transfer, no known asserter, no repeat correspondent, no cascade, no pre-litigation transfer, no bankruptcy sale, no privateering, and no defensive-aggregator terminus. This is the textbook "expired sole-inventor patent, never commercialized, never asserted" profile — the reason it survives in the literature is citation, not monetization.

Per the constraint on honesty: I did not query the USPTO Assignment Center API directly, so I am relying on the Google Patents legal-events mirror plus uspto.report and Justia corroboration. Verify independently at the Assignment Center search page: https://assignmentcenter.uspto.gov/ (Search → Patent Number → 2762913).

I'll verify the citation record for US 2,762,913 directly before analyzing prior art.

Direct answer: US 2,762,913 has no prior-art citations of record

I checked the authoritative source (the granted patent PDF and the Google Patents full-text record you supplied). The reference-citation field is empty. The patent's own text ends the specification with the literal line:

"No references cited."

That is the definitive statement of record for this patent. There is therefore no set of examiner-cited patent citations to walk through, and no reference against which a § 102 anticipation mapping can be drawn from the face of the patent.

⚠️ Contradiction flag (per operating instructions)

Your task premise — "Look at each patent citation for 2762913" — assumes backward prior-art citations exist. The record contradicts that premise. US 2,762,913 issued with zero cited references. I am flagging this rather than manufacturing citations to fill the table.

Evidence the field is empty

• Granted patent PDF (US2762913.pdf): specification ends "No references cited." No "(56) References Cited" block.
• Google Patents full-text record you supplied: the citation block explicitly reads "No references cited."
• Confirmation from later art: Every downstream document that mentions US 2,762,913 lists it as a citation it made, never as the source of a citation. E.g., EP 0341826 A3's search report lists "US 2762913 A 19560911 – JEPSON WILLIAM L" as an [A] (background) cited reference — i.e., the EP examiner cited Jepson, not the other way around.

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The "Cited By" list is not prior art (this is the likely confusion)

The generated Google Patents page shows dozens of entries under "Cited By." Those are forward citations — later patents that cite US 2,762,913 as background. They postdate this patent's 1955/1956 dates and cannot be prior art against it. Representative entries:

All postdate US 2,762,913. None can anticipate it under § 102(a) or (b).

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Independently identified candidate prior art (NOT of record — verify before relying)

Because the examiner cited nothing, I searched the pre-1955 art in the same field. Under the pre-AIA § 102 framework applicable to a June 13, 1955 filing, the relevant window for § 102(b) statutory bars is on/before June 13, 1954, and for § 102(a) before the invention date (no later than June 13, 1955). The most material candidates surfaced are:

1. US 2,509,331 — "Railway train interval detection system" (pub. 1950-05-30)

Most relevant candidate. Retrieved content shows:

• A first transmitter on the head end of each train, "directive in a forward direction," continuously pulse-modulated by a keyer ("short pulses of radio energy").
• A second receiver at the rear end, "directive to the rear," responding to the interrogator frequency and driving a responder transmitter.
• Directional antennas on both ends of both trains (head-end forward, rear-end rearward) — the same "one transmit/receive set per end, aimed outward" architecture as Jepson.
• Checking means that recurrently inject energy from each transmitter back into its own receiver to verify operation — directly material to the self-test subject matter of claim 6.

§ 102 relevance: Potentially anticipatory of the architectural subject matter of claims 1 and 7. But it differs in a way that matters for § 102: it uses two different carrier frequencies (interrogator F1 / responder F2) rather than Jepson's single carrier frequency with two different pulse-repetition rates chosen for deliberate cross-pickup. It also measures distance by pulse time-of-flight (sawtooth/timing), not by received-signal amplitude. So it is material and arguably anticipating as to claims 7 and the tester of claim 6, but does not read on claim 1's "same frequency / two repetition rates" limitation. I could not verify the full text or the named inventor from the retrieved excerpt — treat as candidate, confirm against the PDF.

2. US 2,641,688 — "Radio echo pulse system for vehicles following a fixed route" (pub. 1953-06-09)

Listed among this patent's "Similar Documents." Title and date place it squarely in the same pulse-radar-for-guided-vehicles field and within the § 102(a) window. I could not retrieve its body text to map it claim-by-claim — flagged as unverified.

3. US 2,636,113 — "Fixed route vehicular location and communicating system" (pub. 1953-04-21)

Retrieved content shows a fixed-route pulse system identifying "different ends of a given vehicle or train" and indicating "the speed and direction of other vehicles along the route both ahead and behind." Relevant to Jepson's front/rear identification concept, but it is a transmission-line / wayside-radiating system (B61L3/22), not an all-on-board free-space microwave link. Weak § 102 candidate; strong § 103 context.

4. Older background art (dates from the "Similar Documents" table only)

I have only title and publication date for these — no body text — so I am not asserting any § 102 mapping for them. They are context.

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Bottom line for a § 102 analysis

Caveats

• The zero-citation finding is well-grounded (patent PDF + Google Patents + corroborating EP search report). The candidate prior art in the second half is my own search product, not the examiner's, and must be verified against full text before being treated as anticipation.
• For a rigorous § 102/§ 103 opinion you would pull the full PDFs of US 2,509,331, US 2,641,688, US 2,636,113 and read them against each Jepson claim — I could only retrieve partial text here.
• The ID "2762913" also matches EP 2762913 (ViaSat, "Highly integrated circuit architecture," appl. 14163942.7) and RU 2762913 C1 (Russian arthroscopy-training patent). Per your strict rule, I have not conflated these with US 2,762,913; none is prior art to it.

I'll ground this analysis in the actual prior-art-of-record material on the page. First, let me pull the disclosures of the candidate references.

Let me pull the remaining pre-1955 "Similar Documents" candidates that could actually qualify as prior art.

Obviousness Analysis — US 2,762,913 (Jepson)

0. Scope note and a correction to the record I was handed

Two framing points before the analysis, because they change what "prior art" means here:

(a) The page contains no examiner-cited prior art. The "References Cited" field on US 2,762,913 reads "No references cited." The documents cited against the patent on its Google Patents page are the "Cited By" / forward-citation lists (US 2,831,182; US 3,235,025; US 5,577,469; US 11,814,088 B2, etc.). Every one of those post-dates the June 13, 1955 filing and therefore cannot be § 102 prior art against this patent. They are evidence of later state of the art only.

(b) The usable pool is the "Similar Documents" list (plus general knowledge in the art). Of the ~25 documents there, only the pre-June-13-1955 ones can be § 102/§ 103 art. Filtering by date:

§ 102-eligible (issued before the 1955-06-13 filing):

NOT § 102 art (post-date the filing) — excluded: US 3,041,861 (1962); US 3,152,982 (1964); US 3,112,480 (1963); US 3,366,958 (1968); US 3,605,095 (1971); US 3,663,809 (1972); US 3,691,368 (1972); US 3,691,559 (1972); US 3,993,997 (1976); GB 1,378,689 (1974); US 3,805,056 (1974); DE 69232751 D1 (2002); RU 2001807 C1 (1993).

(c) Governing standard. Filing was 1955-06-13, so the pre-AIA 35 U.S.C. § 103(a) applies, under Graham v. John Deere and KSR Int'l v. Teleflex. A POSA here is a signaling/radio engineer (c. 1955) with several years in pulse-radar and railway carrier-frequency signalling practice, familiar with microwave duplexers/TR cells, pulse coding, and track-circuit detection.

(d) What I actually have. I retrieved substantive disclosure text for US 2,509,331, US 2,477,567, US 2,499,177 and US 2,636,113, and bibliographic confirmation only for US 2,641,688. US 1,787,992, US 1,945,952, US 2,028,497, US 2,083,945, US 2,502,317 and US RE 23,403 E I could not open — I treat them as background corroboration only and flag that explicitly rather than fabricating their contents.

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1. The claims, decomposed

Dependent claim 5 (selector slaved to the vehicle driveline) and claim 6 (by-pass conductor from transmitter to receiver with a periodically-interrupting switch — the self-test) map onto the specification's axle-driven selector and capacitive-pick-off tester.

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2. Ground 1 — Claims 1, 3 and 7 over US 2,509,331 in view of US 2,641,688

2.1 What US 2,509,331 (Railway train interval detection system, 1950) discloses

Its disclosed system maps onto elements B, C, D, E and F almost element-for-element:

• On the head end of each train: a pulse-modulated transmitter driving a forward-directive antenna and a forward-directive receiver antenna; a keyer continuously pulse-modulating the transmitter (element C).
• On the rear end of the preceding train: a rear-directive receiving antenna + receiver, and a receiver-controlled transmitter radiating rearwardly (element B/D).
• An indicator (cathode-ray-tube type) jointly controlled by keyer and receiver, measuring the transit-time interval → distance.
• A recurrent self-check that is defeated when two trains come within range: "checking means which normally operates to check the integrity of the apparatus, and which becomes inoperative during the time that the apparatus is measuring and indicating the distance between two trains" (US 2,509,331). This is the same architecture as element E and as claim 6's periodic tester.
• Coding devices "having contacts which are recurrently operated at a rate substantially less than said pulse rate," plus code-following and code-detecting relays — i.e., pulse-rate coding for distinguishing and validating signals (element C).

2.2 The differences and who supplies them

The evidentiary gap versus claims 1/3/7 is narrow but real:

1. '331 runs two carrier frequencies (an "interrogator" frequency forward, a "responder" frequency back). Claim 1 and claim 7 require all transmitters on the same frequency, with a receiver blanked during local transmission (element E) and the cross-signal still receivable (element F).
2. '331 ranges by time-of-flight, not by received-signal magnitude, so it does not, by itself, suggest the "magnitude = distance / rate of change = closing speed" indication that the specification (and the claim-9/10 reproducer concepts) rely on.

US 2,641,688 (Radio echo pulse system for vehicles following a fixed route, Standard Telephones & Cables, 1953) is the natural supplier. It is a pulse-echo system, which by definition operates transmitter and receiver on a single carrier frequency feeding a common antenna, and therefore necessarily embodies the transmit/receive isolation (element E) — the duplexer/TR-cell arrangement the specification itself names. Its very title places it in the same art (pulsed radio on vehicles constrained to a fixed route). I confirmed the reference and its date/assignee from the citing-document record, but I could not open its full text; the single-frequency/duplexer assertion is from the nature of a pulse-echo fixed-route system plus the patent's own characterisation, not from a verified passage. Treat it as the weakest link in this ground.

Combination, claim-by-element:

2.3 Motivation to combine (the § 103 "why")

Five independent, articulated rationales:

1. Equipment economy and standardisation. The patent itself makes it an object to use "only one type of equipment … identical units … in the front and rear." A single-frequency, single-antenna design directly serves that objective and is a classic known-technique / predictable-variation rationale under KSR.
2. Spectrum and hardware conservation. Collapsing "interrogator" and "responder" channels into one channel halves the RF front ends and antennas — a recognised benefit in a cost-sensitive, weight-sensitive, wind-loading-sensitive railway mounting (the patent's own stated concerns).
3. The duplexer was already a mature microwave component. A POSA combining a pulsed transmitter and a receiver on one antenna would, as a matter of routine engineering, specify a TR cell or equivalent — exactly the "known technique, known elements, predictable result" situation KSR endorses.
4. '331 itself teaches partial blanking. Because '331 already makes its equipment self-check "inoperative" while trains are within range, the notion of selectively disabling a receiver is squarely within the reference; extending it into the transmit interval is a mechanical change in scope, not in principle.
5. Common-problem pairing. Both references address "vehicles on a fixed route that cannot stop within sight distance" — the same field, the same problem, and combinable without any change in the references' respective principles of operation at the system level.

Conclusion on Ground 1: claims 1, 3 and 7 are, in my assessment, more likely than not obvious on this combination, resting on rationales (1)–(4). The single strongest element of doubt is element F.

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3. Ground 2 — Claims 1, 7 and 8 over US 2,477,567 (+ US RE 23,403 E)

US 2,477,567 (Eastern Ind. Inc., 1949) is a vehicle-detection and speed/direction analyser using a single ultra-high/hyper-frequency wave directed along a traffic lane, beating the reflected wave against the transmitted wave. Its disclosure supplies:

• Distance from signal magnitude — the beat frequency is "a function of distance of the reflecting surface from the transmitter-receiver."
• Rate of change of distance = speed, with direction of approach/departure derived from the sense of frequency change.
• A single transmitter-receiver station — i.e., a shared transmit/receive architecture on one frequency (element A/E support).

This reference is the best support for the reproducer aspects — magnitude ∝ distance, its rate of change ∝ closing speed, and an explicit direction indicator — which are the substantive content of dependent claims 9 and 10 (front-vs-rear origin; aural + visual).

On its own, '567 does not disclose vehicle-to-vehicle transmitter pickup, front/rear coding, or a copier/blanking control; it depends on reflection, not a foreign transmitter. So for claims 1/7/8 it is a secondary reference. Its proper role is:

• Cumulative obviousness of claim 1 as to the indicia (distance + rate of change), and
• Primary obviousness of claims 9 and 10 when combined with '331's CRT indicator.

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4. Ground 3 — Claim 8 over US 2,509,331 + US 2,477,567 + US 2,499,177 (the hard one)

Claim 8 is the most interesting, because of its anti-synchronised-blocking limitation: the first (front) generators vary from any of the second (rear) generators by substantially more than same-end generators vary from each other — i.e., deliberately staggered, non-locked repetition rates so that a blanked local receiver still catches the majority of an oncoming same-end train's pulses.

Where the prior art points:

• '331 supplies front-vs-rear rate distinction and coding devices "recurrently operated at a rate substantially less than said pulse rate."
• '567 supplies the purposes the system needs — distance, direction of movement, and a zone selector tuned to a "predetermined beat frequency range," which is conceptually a filter for rejecting out-of-band returns.
• US 2,499,177 (Baughman / Union Switch & Signal, 1950) is directly on point for the self-diagnostic strand: its detector relay "releases in the event of loss of energy or the occurrence of a fault in the detecting system," and its signalling is done at a code frequency through a resonant decoding unit that discriminates one code from another. That is the same conceptual move as using two distinct pulse-repetition rates as distinguishable codes.

The obviousness argument: pulse-radar practice by 1955 had long dealt with mutual interference between pulsed sets and with the receiver "dead time" produced by a duplexer. Given (i) '331's teaching that front and rear signals are coded differently by rate and that a checking function is blanked while ranging, and (ii) '177's teaching that coded tones may be selectively decoded, a POSA who chose to move to a single frequency would foresee the exact defect the patent solves — two same-end sets blanking each other in lock-step — and the fix (make the free-running rate non-identical so the trains drift out of coincidence) is the kind of "predictable variation of a known technique" that KSR holds obvious. The specification itself concedes the remedy is simply to use "free running unstabilized generators having repetition rates that continuously vary slight amounts about the design rate" — i.e., it relies on component tolerance, not on a new structure.

Where I would expect the patentee to fight: there is no expressly articulated prior-art recognition of the "synchronised blocking" failure mode. Building a § 103 case on "a POSA would have foreseen an unarticulated failure mode" is exactly what KSR permits ("the subject matter of the patent need not be disclosed in any particular way") but what a fact-finder may nonetheless reject as hindsight. I rate claim 8 as closer to the line than claims 1/3/7 — arguable either way, leaning obvious.

⚠️ Caveat I must repeat: the Google Patents OCR of claim 8 is garbled and its final two clauses are reciprocally duplicative, as noted in the patent-summary section above. My reading — asymmetric spacing between the two families of generators — may not match the printed claim. Verify against the original patent PDF before relying on any claim-8 conclusion.

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5. Ground 4 — Claims 6, 9 and 10

• Claim 6 (by-pass self-test conductor + periodically-interrupting switch). This is squarely anticipated as a concept by US 2,509,331 ("checking means … for recurrently causing each transmitter to supply radio energy … to the receiver associated with the transmitter, and means for detecting the recurrent operation of the receiver by this energy") and reinforced by US 2,499,177 (detector relay releases on "loss of energy or the occurrence of a fault"). The patent's specific implementation (capacitive pick-off 66 → level-set resistor 70 → relay 67 periodically connecting past the duplexer to receiver input 71) is an electrical-engineering detail within the ordinary skill level; the claimed functional result is already in '331. Likely obvious.
• Claims 9 and 10 (front/rear-distinguishing reproducer; aural + visual). US 2,509,331 provides a visual indicator (CRT trace). US 2,477,567 provides direction-of-movement indication. US 2,636,113 expressly identifies "different ends of a given vehicle or train" and indicates "the speed and direction of other vehicles along the route both ahead and behind." Adding an audible alarm beside a visual one in 1955 railway apparatus is a predictable, conventional combination (and the patent's own claim-10 language is bare "aural and visual indicating means"). Likely obvious; low-strength dependent claims.
• Claim 5 (selector slaved to the driveline). The spec admits the alternative — "manually controlled or means operated from a portion of the train drive system, such as an axle" — is a mere design choice. Slaving an existing electrical selector to an axle to sense direction of travel is a predictable mechanical expedient.

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6. Counter-argument the patentee would raise (and how it fares)

Teaching away / change of principle of operation (impermissible "bodily incorporation").

• '331 uses two different carrier frequencies. One can argue that '331's interrogator/responder split is essential to its transponder ranging — the responder must transmit on a frequency the interrogator's own receiver is not blanked against — so a POSA reading '331 is steered away from collapsing everything onto one frequency, and the modification would destroy '331's principle of operation.
• '331 ranges by time-of-flight; the patent ranges by magnitude. A combination that changes the ranging physics is vulnerable to the argument that the references are being used outside their principles.

How it fares under KSR: moderately well, but not decisively. The "change in principle of operation" doctrine has been substantially narrowed; where a reference is used only for what it fairly teaches (here, front/rear directional pulsed signalling with blanked self-check) rather than for its core ranging physics, the objection weakens. And the motivation for the change — standardisation and economy — is the patent's own stated object, which makes "why would you do this?" answer itself:

"It is a further object of the invention to provide a warning system in which only one type of equipment is required and identical units are installed in the front and rear of each vehicle using the system."

Stated objectives of that generality are precisely what KSR treats as design incentives rather than inventive contributions.

Secondary considerations. I identified no evidence of nexus-bearing objective indicia — no commercial success, no licensing, no industry praise, no copying; the patent is a single-inventor, unassigned, never-enforced grant with "No references cited" and an expiry in 1973. Absent such evidence, the Graham secondary factors do not rebut the prima facie case.

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7. Bottom line

The single feature that would carry a § 103 defence today is the deliberately staggered, free-running repetition rates that defeat synchronised blanking (claims 2/8) — and even that is weakened by the specification's own admission that it is achieved by ordinary "unstabilized" component tolerance rather than by structure.

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8. Explicit uncertainties

1. Prior-art set. I was limited to the documents on the supplied page. A real § 103 challenge would also draw on the c. 1945–1955 non-patent literature (radar duplexing, staggered-PRF, railway carrier signalling) that the page does not contain and that I have not searched.
2. US 2,641,688. I confirmed its number, title, assignee and 1953-06-09 issue date (from citing-document records) but could not open its full text. My characterisation of it as a single-frequency pulse-echo system with T/R isolation is based on the reference's own title and the nature of pulse-echo ranging, not on a verified passage. This is the softest link in Grounds 1–3.
3. US 1,787,992, US 1,945,952, US 2,028,497, US 2,083,945, US 2,502,317, US RE 23,403 E. Not retrieved; excluded from the substantive mapping. They could only strengthen the obviousness case.
4. Claim 8 OCR. As flagged in the earlier section, the printed text of claim 8 appears defective in the Google Patents transcription; my construction of its rate-spacing limitation is provisional.
5. No litigation, no PTAB, no reissue, no reexamination exists to supply an adverse administrative construction of any term — so all claim-construction positions above are mine, not the Office's.
6. Practical irrelevance caveat. US 2,762,913 expired 1973-09-11. This § 103 analysis is therefore academic/historical (e.g., for invalidity-contentions in a later patent that cites it, or for prior-art-dating exercises) rather than a live invalidity posture.

Sources relied on: US 2,762,913 full text (https://patents.google.com/patent/US2762913/en); US 2,509,331 (https://patents.google.com/patent/[US2509331A](/patent/US2509331A)/en); US 2,477,567 (https://patents.google.com/patent/[US2477567A](/patent/US2477567A)/en); US 2,499,177 (https://patents.google.com/patent/[US2499177A](/patent/US2499177A)/en); US 2,636,113 (https://patents.google.com/patent/[US2636113A](/patent/US2636113A)/en); US 2,641,688 (bibliographic record only).