US 6145792

I'll search for this specific patent number and related litigation records.

Let me search specifically for CAFC 2026 dockets and any litigation involving this patent.

I have gathered sufficient data. Let me do one final check for any CAFC docket activity specifically.

Search results for US 6,145,792

Important preliminary note on scope: My searches of the patent databases and litigation dockets surfaced no CAFC (Federal Circuit) 2026 docket naming this patent. The only 2026-era record in which the string "6145792" appears is a PTAB proceeding — IPR2026-00134 (Petitioner: Westinghouse Air Brake Technologies Corporation), concerning U.S. Reissue Patent RE47,835 — where "6145792" appears only inside prior-art search strings quoted from the RE47,835 file history, not as the challenged patent. I could not confirm any live CAFC appeal involving 6,145,792. Treat that as an explicit uncertainty rather than a negative finding, since I cannot rule out a docket I did not retrieve.

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Bibliographic data (from the patent record)

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Abstract

A warning system and method for warning a train operator that the train is approaching personnel at a railroad station. A transmitter disposed at the railroad station transmits a radio frequency (RF) warning signal with a given power output. A receiver on the train receives the RF warning signal and generates an alarm to notify the train operator of the presence of the personnel. A transmitter on the train transmits an RF confirmation signal upon receipt of the RF warning signal by the train receiver. A receiver disposed at the railroad station receives the RF confirmation signal and generates an alarm to notify the personnel that the train operator is aware of their presence.

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Plain-language overview of the independent claims

Claim 1 — System (four cooperating elements):

1. Worker-side transmitter — located adjacent personnel near the tracks, continuously sends an RF warning signal over a wireless path. The signal's power output is dependent on the speed of the train, and the signal itself indicates that personnel are present on/near the tracks.
2. Train-side receiver — receives the warning signal a predetermined amount of time before the train reaches the personnel, where that time is a function of the signal's power output; on receipt it triggers an alarm (any form) telling the operator that personnel are present.
3. Train-side transmitter — sends an RF confirmation signal back once the train receiver has received the warning.
4. Worker-side receiver — receives the confirmation and triggers an alarm telling the personnel that the operator has seen/acknowledged the warning.

In short, a closed-loop "worker-broadcast / train-acknowledge" RF safety loop, with the timing guarantee engineered through transmit power keyed to train speed.

Claim 7 — System (portable variant): Same four-element architecture as claim 1, but the worker-side transmitter is expressly a portable transmitter carried by at least one worker, and the worker-side receiver is expressly a portable receiver carried by that worker (i.e., a body-worn pager/vest-type device rather than fixed station equipment). It retains the "power output dependent upon the speed of the train" and "predetermined amount of time dependent upon power output" limitations.

Claim 8 — Method (corresponding steps):
transmit an RF warning at a power output dependent on train speed, from personnel near the tracks → receive it on the train a predetermined time ahead of arrival (that time dependent on the power output) → generate an alarm for the operator → transmit an RF confirmation from the train → receive the confirmation at the personnel side → generate an alarm telling the personnel the operator is aware of them.

Dependent claims (scope extensions):

• Claims 2–6: the worker-side transmitter is portable; the worker-side receiver is portable; the train alarm is visual, audio, or vibratory (respectively).
• Claims 9–10: method variants in which the warning is transmitted by a portable worker-carried transmitter and/or the confirmation is received by a portable worker-carried receiver.

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Notable technical/prosecution details from the specification

• RF warning carrier is preferably 900–980 MHz (designated beeper/pager bands), continuously transmitted while workers are on/near the tracks; transmitter is a variable-output device.
• The specification frames the power/timing rule in terms of maximum allowable speed ("dependent upon the assumption that train 12 is travelling at its maximum allowable speed"), whereas the granted independent claims recite power "dependent upon the speed of the train." That gap between the disclosure's "maximum allowable speed" framing and the claims' broader "speed" wording is a potential claim-construction sensitivity worth flagging.
• The "predetermined amount of time" is exemplified as at least fifteen seconds.
• Optional encoder/decoder coding of the warning signal is described to prevent false alarms from RF interference or illicit transmissions.
• Alarm modalities: visual display (flashing lights, alphanumeric messages), audio, vibratory.
• Background cites the applicants' own earlier U.S. Pat. No. 5,727,758 (tactile and audible warning system for railroad workers), whose stated shortcoming (workers warned, operator not) is the problem this patent addresses.

Prior art and citation footprint

• Cited by the examiner (16 references) includes US 2,762,913 (Jepson); DE 2405408 (Philips); several Japanese Kokai (JPS 52-35504, JPS 63-315369, JPH 4-126664, JPH 4-163273, JPH 6-1239); DE 4219067 (Wetzler); US 5,303,259 (Loveall); WO 94/21504; US 5,415,369 (Rockwell, in-cab signaling w/ RF digital transmissions); US 5,461,366 (CORIS remote alarm); US 5,554,982 (Hughes, wireless train proximity alert); US 5,572,201 (Federal Signal); US 5,620,155 (Michalek); and US 5,727,758 (Penza).
• Cited as prior art by later patents — US 6,145,792 shows up in the prior-art tables of, e.g., US 10,518,792 (Miller Felpax), US 8,590,844 (Siemens/Invensys), US 8,500,071 (Invensys), and US 7,624,952 (Bartek), among others in the track-worker safety field.

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Bottom line / caveats

• Confirmed, authoritative data for 6,145,792: title, inventors (George Gregory and George Robert Penza), filing and issue dates, abstract, and claim structure.
• Assignee: The record lists an individual (no corporate assignee recorded). I have no assignment-history document confirming any change of ownership; treat "Individual" as the database-listed status only.
• Litigation: I found no verified CAFC 2026 docket for this patent. The only 2026-related hit is a PTAB IPR (IPR2026-00134) about RE47,835 in which 6,145,792 appears solely as a searched prior-art string. Given the patent's expired status (2018), it is unlikely to be an infringement suit target, though it remains citable art in validity fights over later worker-protection patents.

I'll research litigation involving US Patent 6,145,792 across patent litigation databases.

Let me search more specific litigation databases.

Litigation Search Report — U.S. Patent No. 6,145,792

Patent: U.S. 6,145,792 — "Railroad worker warning system for train conductors"
Inventors: George Gregory Penza; George Robert Penza
Assignee: Individual (unassigned)
Filing date: April 29, 1998 | Grant: November 14, 2000
Legal status: Expired – Lifetime (anticipated expiration April 29, 2018; maintenance fees paid at years 4, 8, and 12)

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Finding: No litigation identified

I found no record of any patent infringement litigation — or any other court proceeding — involving U.S. Patent 6,145,792.

That is, there is no known case in which the '792 patent was asserted as a claim in a U.S. district court (PACER/Docket Alarm), before the Court of Appeals for the Federal Circuit, or in an ITC Section 337 investigation, and no known declaratory-judgment action involving it.

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What I did find (and why it is not litigation)

Every search hit referencing "6145792" fell into one of three non-litigation categories. I am flagging these explicitly so they are not mistaken for case activity:

1. Prior-art citation in later patent applications/patents. The '792 patent is cited on the face of numerous later railroad worker–safety patents (e.g., Metrom Rail, Harsco, Miller Felpax, Bombardier, Siemens). For example, it appears as a cited reference in U.S. 10,518,792 (Miller Felpax), U.S. 8,590,844 (Siemens/Safetran), U.S. 9,248,849, and U.S. 11,780,481 (Metrom Rail). Citation is not litigation.

2. Prior-art reference inside PTAB/IPR proceedings about other patents. The most prominent hit was an exhibit in IPR2026-00134, Westinghouse Air Brake Technologies Corporation (Petitioner) — but that proceeding concerns a different patent (RE47,835, a Railware, Inc. patent). The string "6145792" appears only as part of the petitioner's prior-art search queries (e.g., "("6145792" | "7624952").URPN"). Likewise "6145792" appears in a Siemens-related PTAB petition exhibit. In both instances the '792 patent is being used as prior art against someone else's patent — not being asserted.

3. Third-party patentability/novelty searches. A PCT search report (WO2012031321A1, QR Limited) cites US 6145792 A (Penza et al.) under category "X." Again, this is a citation, not a lawsuit.

I also note a completely unrelated numeric coincidence: a Lithuanian registry filing (MB "Būk sumanus") bears internal notice number "6145792." Interpreted literally, this is not the patent.

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Important caveats on this report

• Not a substitute for a PACER/Docket Navigator/PACERPro run. I did not have authenticated live access to PACER, the Unified Patents litigation portal, or Docket Navigator during this search. My conclusion rests on broad open-web searching, which surfaced no affirmative assertion of the '792 patent. A subscription litigation database should be queried to confirm before relying on this for a freedom-to-operate or clearance opinion.
• Practical context supporting the "no litigation" conclusion: the patent named individual inventors with no corporate assignee, expired on April 29, 2018, and its prosecution family consists of a single U.S. application (US09/069,132). There is no foreign family and no reported assertion activity. A patent that was never asserted before expiration would be consistent with the absence of litigation records.
• Do not conflate with related Penza patents. The inventor's earlier U.S. 5,727,758 and U.S. 5,924,651 ("Tactile and audible warning system for railroad workers") appear in "similar documents" listings and as citations; those relationships reflect common inventorship and citation, not litigation involving the '792 patent.

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Bottom line: As of the searchable record, there is no known litigation involving U.S. 6,145,792. If you require a litigation-grade clearance conclusion, I recommend an authenticated PACER docket search and a Docket Navigator / Unified Patents run keyed to the exact patent number "6145792," which I could not complete here.

Proceedings overview

Total AIA trial proceedings on US 6,145,792: 0. The USPTO Open Data Portal returns no IPR, PGR, or CBM petitions against this patent, and my web searches (Google Patents, Docket Alarm, uspto.report, PTAB-related hits) surfaced no PTAB trial, no institution decision, no Final Written Decision, and no Federal Circuit appeal concerning it. There is therefore no breakdown by status to give — nothing was invalidated, nothing was sustained, nothing settled, and nothing was denied institution, because nothing was ever filed. The defensive posture implication is unusual and worth stating plainly: this is not a "hardened" patent in the sense of having survived attacks; it is an abandoned-asset patent. All ten claims are legally UNTESTED at the PTAB, but the patent expired on 2018-04-29 (20-year term from the 1998-04-29 filing, per the Google Patents legal-status record: "2018-04-29 Anticipated expiration"), so the practical exposure is limited to past damages for pre-expiration conduct.

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Proceedings

No proceeding numbers can be listed. Per the operating rule against inventing proceeding numbers, I am not populating per-proceeding entries for proceedings that do not exist.

None on file

• Type: N/A — no Inter Partes Review, Post-Grant Review, or Covered Business Method review has been filed against US 6,145,792.
• Filed: N/A
• Status: N/A (source: "PTAB proceedings on file" structured block — USPTO ODP API returns no AIA trial proceedings as of the most recent ingest)
• Judge panel: N/A
• Petition grounds: N/A — no petition exists
• Institution decision: N/A
• Final Written Decision: N/A — there is no FWD to quote or characterize, so I make no claim-by-claim finding. Claims 1, 7 (independent system claims), claim 8 (independent method claim), and claims 2–6 and 9–10 (dependent) are all UNTESTED at the PTAB.
• Settlement / termination: N/A
• Appeal: None. No FWD means no CAFC docket number exists. Nothing on CourtListener.
• Defensive value: Because no IPR was ever filed, there is no § 315(e)(2) estoppel, no cancellation, and no PTAB record to leverage against a demand letter. A defendant's leverage on this patent comes from the expiration date, not from any trial outcome.

⚠️ Near-miss hits I checked and excluded (do not cite these as proceedings on 6,145,792)

Two Docket Alarm records surfaced under searches for "6145792" that a careless read could mistake for activity on this patent:

• IPR2026-00133 — Westinghouse Air Brake Technologies Corporation (Exhibit-1001 is US 9,517,782, "Tools for railway traffic control," Railware, Inc.). US 6,145,792 appears only as a cited reference in the '782 patent's specification.
• IPR2026-00134 — Westinghouse Air Brake Technologies Corporation (Exhibit-1002 is the file history of US RE47,835). US 6,145,792 appears only inside examiner search-string strings in that file history (e.g., ("6145792").PN).

In both cases the patent under challenge is a different patent; 6,145,792 is prior art cited within it. Neither IPR2026-00133 nor IPR2026-00134 is a proceeding against US 6,145,792, and neither should be represented as such to a court or an adversary. (I could not independently retrieve the E2E dockets behind these Docket Alarm URLs within my search budget, so treat the petitioner/patent identifications above as search-derived, not E2E-verified.)

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Strategic summary

Claim status. All claims of 6,145,792 — independent claims 1 and 7 (system) and 8 (method), plus dependent claims 2–6 and 9–10 — are UNTESTED, not canceled and not sustained. There is no PTAB narrowing and no surviving-claim carve-out to point to, because no tribunal has construed a single term of this patent. The claim set as granted is what you would be facing, if anyone were facing it. The patent was maintained to full term: Google Patents shows maintenance fee payments at the 4-, 8-, and 12-year intervals (2004-02-12, 2008-05-06, 2012-05-14) and expiration only by operation of the 20-year term, not for non-payment. Expired-Lifetime status is current.

Estoppel landscape. There is no § 315(e)(1) or (e)(2) estoppel to leverage — estoppel attaches only to a petitioner that filed and completed a trial, and no one did. That cuts both ways: a defendant today is free to run any § 102/§ 103/§ 112 ground, in any forum, without worrying about a prior petitioner's record. The flip side is that there is no PTAB record of institution to point a court to, which in district-court practice means no § 315(a)/b-driven stay argument and no Patent Trial and Appeal Board credibility dividend. Any validity fight is a fresh, first-instance fight over the granted claims. Note that on this record the art cited on the face of the patent is substantial and largely predates the 1998 priority date — US 2,762,913 (Jepson), US 5,555,982 (Shirley), US 5,462,366, US 5,303,259, US 5,620,155, DE 2,405,408, and applicants' own US 5,727,758 — and later patents in the field (e.g., US 7,624,952, US 8,346,877, US 8,956,789, WO 2012/031321) describe worker-warning systems with bidirectional train-operator/worker alerting, which is the core of claim 1. None of that has been tested in a PTAB trial.

Pattern signals. No pattern exists: no serial petitioner, no defensive aggregator (I found no Unified Patents or RPX involvement), no Patent Owner appeal activity, and no parallel proceeding of any kind. Solely for accuracy of the record: patent owner is listed as Individual (inventors George Gregory Penza and George Robert Penza), and the patent is a follow-on to the same inventors' US 5,727,758 and a sibling of US 5,924,651 — a small, self-prosecuted family rather than a portfolio that attracts PTAB attention. That is consistent with the absence of IPRs: well-asserted patents eventually attract IPRs, and this one apparently was never asserted at scale.

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Recommended next steps

1. If you received a demand letter citing US 6,145,792, check the expiration date first. The patent expired 2018-04-29. There can be no prospective infringement and no injunction; any recovery is past damages for infringing acts before that date, further capped by the six-year lookback of 35 U.S.C. § 286 (i.e., acts on or after ~2012-10-01, if suit were filed today). Also verify whether the asserted conduct even falls in that window — pre-2018 sales of worker-warning hardware, not current ones.
2. There is no FWD to link to, and you should say so explicitly in any invalidity contentions or motion practice rather than implying a PTAB outcome. If opposing counsel represents that an IPR invalidated or sustained these claims, that representation is unsupported — the ODP shows zero AIA trials and my searches found none.
3. If a live IPR is contemplated (unlikely given expiration): the one-year bar of § 315(b) runs from service of a complaint alleging infringement, and an expired patent can still be challenged in IPR but is construed under Phillips with no possibility of claim amendment — a poor economics case against a patent with no forward-looking value. Absent a pending served complaint, the practical path is § 282 invalidity in district court or, more likely, a damages/expiration-based dismissal.
4. Do not cite IPR2026-00133 or IPR2026-00134 as proceedings on this patent. As noted above, those Westinghouse Air Brake petitions concern US 9,517,782 and RE47,835 respectively; 6,145,792 is merely prior art cited inside them.
5. Watch item: the Google Patents "Cited By" table shows a large and active downstream field (Metrom Rail, Harsco, Bombardier, Siemens, Miller Felpax) that repeatedly cites 6,145,792 as background art. That traffic is citation, not challenge. If a member of that field were ever to acquire the patent and assert it, an IPR would likely follow — and given the expired status, a Phillips-construed IPR on the on-face art (Jepson, Shirley, Michalek) would be the natural vehicle.

Verification caveat: the negative finding rests on (a) the structured ODP block, which is authoritative here, and (b) web searches that did not surface any PTAB proceeding involving this patent number as the subject patent. I did not have a working, E2E-verified docket lookup for US 6,145,792 within my tool budget, so if the stakes warrant it, confirm directly at USPTO PTAB E2E and the patent's Google Patents page before relying on the negative in a filing.

I'll start by verifying the assignment record and inventor/assignee context from multiple sources.

I hit my tool-call limit before I could load the Assignment Center UI directly, so let me be explicit about the evidence base for what follows.

Evidence base and its limits: I searched the indexed assignment/legal-events data (Google Patents legal events for US6145792A, third-party mirrors, PTAB/Unified Patents document excerpts). I could not directly load assignmentcenter.uspto.gov (interactive, session-based), so I cannot quote reel/frame numbers for this patent — because there appear to be none. I also could not verify correspondents of record, because a correspondent only exists if a recording exists. Anything below not grounded in the sources listed is flagged as unverified rather than asserted.

Inventors

Pattern notes:

• The two inventors share a surname and appear together across the small Penza family (US 5,727,758 / 5,924,651 / 6,145,792), consistent with a family or close-partner garage/small-entity operation rather than a corporate R&D group.
• The "inventors departing the assignee within 12 months" pattern is inapplicable: there is no original corporate assignee to depart from. No inventor-to-employer assignment was recorded.
• Unverified lead: patent listing sites show a "George, Gregory Penza" named as an inventor on ULC Robotics, Inc. filings (pipeline maintenance, roughly 2015 vintage) at the same time the rail patents were 15+ years old. Same-name match only — I did not verify this is the same person, and it post-dates this patent by nearly two decades.

Original assignee

None — the patent issued to the inventors as individuals. Google Patents lists both "Original Assignee: Individual" and "Current Assignee: Individual" for US6145792A, and application 09/069,132 was filed 1998-04-29 by individual inventors with no recorded assignment to any company, university, or other entity.

• Product embodying the claims: No corporate record exists to assess. The specification describes a portable RF transmitter carried by track personnel plus an in-train receiver that returns an RF confirmation signal — a two-way radio worker-protection product. Nothing in the record shows a commercialized product from a named entity.
• Primary line of business: N/A (individual inventors). The patent's own field-of-use framing is railroad/subway signals and switches, and the specification specifically pitches subway tunnels and elevated track "where egress from the track is limited."
• Current status: The patent is Expired — Lifetime, with anticipated expiration 2018-04-29 (20 years from filing). Critically, the last recorded fee event is the year-12 maintenance fee paid 2012-05-14 (Google Patents legal events, FPAY series 2004-02-12 / 2008-05-06 / 2012-05-14). That means the patent was maintained to its full term — it expired by reaching end of term, not by lapsing for non-payment of fees. There is no "LAPS"/"STCH — expired due to nonpayment" event in this patent's record (contrast, e.g., US 5,924,651, which lapsed for fee non-payment effective 2010-04-07).

Assignment timeline

There are no recorded assignments for US 6145792. I found no assignment (AS) legal-event entries for this patent in any indexed source, and no reel/frame records to report.

This is a substantive finding, not a gap in searching: Google Patents' legal-events feed does surface assignment recordings when they exist — the same feed shows an AS event with reel/frame 008305/0958 for the unrelated US 5,924,651 page. US6145792's feed contains only:

• 2000-10-27 — STCF, "Information on status: patent grant" (posted at grant)
• 2004-02-12 — FPAY, year-of-fee-payment 4
• 2008-05-06 — FPAY, year-of-fee-payment 8
• 2012-05-14 — FPAY, year-of-fee-payment 12

Translation: the chain never left the original inventors. No security agreement, no merger, no change of name, no license recordation, no NPE transfer, no defensive-aggregator acquisition. There is therefore no correspondent of record to capture — the single most useful tell you asked me to track is absent by definition here.

Per your instruction, I would normally stop here. I'm continuing with the remaining sections because the requested output format requires them and because "no chain" is itself an informative verdict — but everything below is constrained by the absence of reel/frame evidence.

Timeline diagram

timeline
    title Ownership of US 6145792
    1998 : Filed by two individual inventors
    2000 : Patent granted to inventors personally
    2004 : Maintenance fee year 4 paid
    2008 : Maintenance fee year 8 paid
    2012 : Maintenance fee year 12 paid
    2018 : Patent expires at end of term

NPE / troll-pattern signals

Unverified lead, deliberately not scored: a Unified Patents portal page for the sibling patent US-5924651-A displays the name "Harsco Technologies LLC" near that patent's bibliographic data. I could not confirm whether that is an ownership field or (more likely, given that Harsco Technologies appears as the assignee of later patents that cite the Penza family — e.g., US 10,913,472 and US 2016/0096539) simply a citation-context artifact on the portal. I am flagging it as unclear and recommending direct verification against Assignment Center reel/frame before anyone treats Harsco as a record owner of the Penza patents.

Verdict

Insufficient data — which in this case is the equivalent of non-asserting, inventor-held.

Justification: the record contains zero recorded assignments. The only legal events for US 6,145,792 are the grant (STCF, 2000-10-27) and three maintenance-fee payments (2004-02-12, 2008-05-06, 2012-05-14), and the patent expired at the end of its 20-year term on 2018-04-29 still in the names of George Gregory Penza and George Robert Penza. With no reel/frame entries, no assignee entity, no correspondent of record, and no assertion activity — only prior-art citation in later rail-safety proceedings — none of the eight NPE signals can be marked present, and the headline NPE predicates (shell transfer, asserter assignee, repeat correspondent) are structurally impossible on this record. A caveat on rigor: I could not open the Assignment Center itself, so I am inferring from mirrored legal-events data that surfaces AS recordings when they exist; if you need a print-quality confirmation, verify at the USPTO Assignment Center search (https://assignmentcenter.uspto.gov/) and the Google Patents legal-events tab (https://patents.google.com/patent/US6145792A/en#legalEvents), searching by patent number 6145792 and by application 09/069,132.

This is a clean, individually-held, small-entity patent that was never monetized through an assignment chain — the interesting story in this family is prosecution (the §102/§103 family overlap with the inventors' own US 5,727,758, which the specification expressly distinguishes) rather than ownership.

I'll research this patent and its cited prior art. Let me run several searches.

Let me gather details on the remaining cited references.

Prior-Art Analysis: US 6,145,792

"Railroad Worker Warning System for Train Conductors"

Verification note on the search target. The strict instruction was to search for patent number 6145792 and to interpret identifiers literally. My searches returned matching records for US 6,145,792 (application US 09/069,132), consistently identified across Google Patents, Justia, and third-party databases as "Railroad worker warning system for train conductors," inventors George Gregory Penza and George Robert Penza, original assignee Individual, filed 1998-04-29, granted 2000-11-14, priority date 1998-04-29, legal status Expired – Lifetime (anticipated expiration 2018-04-29). No conflicting record for a different "6145792" appeared. I did not directly retrieve a uspto.gov PatentCenter/PAIR page in the search results returned; the confirmation above comes from Google Patents (patents.google.com/patent/US6145792A/en), Justia, and the patent's own front page. I flag that limitation rather than imply a PAIR lookup occurred.

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1. The patent at issue — claim architecture

The disclosure (best mode) covers a worker-carried transmitter 24 that continuously emits an RF warning signal (preferably 900–980 MHz), a train-mounted receiver 28 that actuates visual (34), audio (38), or vibratory (42) alarms, and — the distinctive addition over the inventors' earlier work — a train-mounted transmitter 46 that sends an RF confirmation signal back to a worker-side receiver 50/62, which alarms the workers that the operator has received the warning. The RF warning signal is transmitted at a variable power output selected as a function of the train's maximum allowable speed so the operator is warned at least a predetermined time (~15 seconds) before reaching the workers.

The independent claims are claim 1 (system), claim 7 (system, portable TX/RX variant), and claim 8 (method). Claims 2–6 and 9–10 are dependent (portable transmitter, portable receiver, visual/audio/vibratory alarms).

The critical inventive hook for § 102 purposes is the bidirectional "confirmation" loop — i.e., personnel→train warning plus train→personnel acknowledgment — combined with speed-dependent transmit power.

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2. Cited prior art — reference-by-reference

All 16 references below are from the patent's own "Citations" list (front-page references cited by/considered during prosecution). Dates are filing/publication as listed for US 6,145,792.

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Reference 1 — US 2,762,913 A (Jepson)

Full citation: William L. Jepson, "Railway train proximity warning system," US 2,762,913, filed Jun. 13, 1955, issued Sep. 11, 1956.
Description (from full text): Trains carry RF transmitters and receivers; pulsed carrier signals are exchanged between locomotives/front-and-rear units. Wayside "observers" receive the pulses; a receiver output drives an audio tone (speaker 64), a visual lamp (60), and a signal-magnitude meter (63), with frequency distinguishing front vs. rear-end units. A timer/relay test circuit (66–81) periodically injects a sample of the transmitter output back into the receiver to self-check both transmitter and receiver.
§ 102 assessment: General train-proximity RF warning art. It discloses RF transmission, a receiver producing audible and visual alarms, and a periodic self-test/feedback path. It is not directed to warning roadway/personnel of a train, contains no worker-carried transmitter, and no train-operator alarm. Cannot anticipate claim 1, 7, or 8. It is, at most, background art potentially combinable against dependent-alarm claims (4–6), but its feedback path (TX-output sampled to own RX) is not the claimed cross-station confirmation. No § 102 anticipation.

Reference 2 — DE 2,405,408 A1 (Philips Patentverwaltung)

Full citation: Philips Patentverwaltung, "Portable railway warning system — has automatic detectors for trains and central reception and alarm station," DE 2,405,408 A1, filed Feb. 5, 1974, published Aug. 7, 1975.
Description (title/abstract-level): A portable railway warning arrangement using automatic train detectors feeding a central reception-and-alarm station.
§ 102 assessment: Discloses portable-worker/stationside warning with detectors and a central alarm — conceptually adjacent to the disclosed control base 56 embodiment and its alarm. It lacks the worker-carried transmitter, the train-side receiver, and (decisively) the confirmation signal. No anticipation of claims 1/7/8; only marginal relevance to the control-base alarm concept.

Reference 3 — JP S52-35504 A (Nakagawa Denki Kogyo KK)

Full citation: Nakagawa Denki Kogyo KK, "Safety unit built-in train approach informing broadcast equipment," JP S52-35504 A, filed Sep. 12, 1975, published Mar. 18, 1977.
Description (as characterized in US 5,727,758's background): A railroad safety system that informs passengers on a platform of an incoming train — a track-mounted detector generates an audible alarm at the platform when a train passes over it.
§ 102 assessment: Warns a fixed location's occupants (passengers), not a train operator, and relies on track-mounted detection rather than a portable transmitter. The '792 specification expressly distinguishes this reference ("a more direct and a quieter way is needed… does not intrude upon the tranquility"). No § 102 anticipation.

Reference 4 — JP S63-315369 A (Mitsubishi Electric Corp)

Full citation: Mitsubishi Electric Corp, "Protecting radio system," JP S63-315369 A, filed Jun. 17, 1987, published Dec. 23, 1988.
Description: Title/abstract-level only in the retrieved record — a radio-based protection/safety system. I could not retrieve a substantive machine translation of the disclosure within the search budget, so I cannot responsibly map it to specific claim elements.
§ 102 assessment: Insufficient information to assert anticipation. Listed only as a considered reference; without the disclosure text I will not speculate.

Reference 5 — JP H04-126664 A (Oki Electric Ind Co Ltd)

Full citation: Oki Electric Ind Co Ltd, "Train approach alarm system," JP H04-126664 A, filed Sep. 19, 1990, published Apr. 27, 1992.
Description (as characterized in US 5,727,758's background): A railroad communication system in which a track supervisor receives an RF train-passage signal and then transmits an RF alarm signal to alarm receivers carried by each worker; each alarm receiver checks the alarm signal to determine whether it is addressed to its own station — i.e., coded/addressed messaging to portable worker receivers.
§ 102 assessment: This is the most relevant of the Japanese references. It discloses (a) portable worker-carried RF alarm receivers and (b) coded, addressable signals. It speaks to the '792's discussion of encoder/decoder coding and to claim 3 / claim 10 (portable receiver). However, the signal path is train→supervisor→worker; there is no train-operator alarm and no train→worker confirmation return loop from a train transmitter. No anticipation of claims 1/7/8; potentially relevant only as secondary art against the coding/portable-receiver features.

Reference 6 — JP H04-163273 A (Mitsubishi Cable Ind Ltd)

Full citation: Mitsubishi Cable Ind Ltd, "Train approach alarming device," JP H04-163273 A, filed Oct. 24, 1990, published Jun. 8, 1992.
Description: Title/abstract-level — a train-approach alarming device (wayside/worker warning). No full text retrieved.
§ 102 assessment: Insufficient disclosure retrieved to map to claim limitations. Consistent with the general "train-approach alarm" family, but no basis for an anticipation finding.

Reference 7 — JP H06-1239 A (Toshin Sangyo KK)

Full citation: Toshin Sangyo KK, "Train approach warning device," JP H06-1239 A, filed Jul. 23, 1991, published Jan. 11, 1994.
Description: Title/abstract-level — train-approach warning device. No full text retrieved.
§ 102 assessment: Same as above — insufficient basis; no anticipation asserted.

Reference 8 — US 5,303,259 A (Loveall)

Full citation: Peter S. Loveall, "Frequency-hopped electronic signal transmitter," US 5,303,259 A, filed Nov. 7, 1991, issued Apr. 12, 1994.
Description: A frequency-hopping RF transmitter architecture for robust, interference-resistant signaling.
§ 102 assessment: Purely a transmitter-physics/anti-interference reference. It supports the '792's stated goal that the receiver "is not susceptible to premature alarm activation due to outside RF interference," and its codable/hopped waveform relates loosely to the encoder/decoder discussion. It discloses none of the system topology (worker TX, train RX, confirmation link, personnel alarm). No anticipation of any independent claim.

Reference 9 — DE 4,219,067 A1 (Wetzler)

Full citation: Gerd R. Wetzler, "Warning personnel and vehicles in track area of railway lines…," DE 4,219,067 A1, filed Jun. 11, 1992, published Dec. 16, 1993.
Description (title): Warns personnel and vehicles in the track area against approaching, passing, and departing rail vehicles by a source producing continuous body (structure-borne) sound signals in the track rails.
§ 102 assessment: Directed to warning persons/vehicles, not train operators; uses rail-borne acoustic signaling, not worker-carried RF transmitters, and has no confirmation channel. No anticipation of claims 1/7/8.

Reference 10 — WO 94/21504 A1 (EBS GmbH für Eisenbahnsicherung)

Full citation: EBS GmbH für Eisenbahnsicherung & Co. KG, "Optical warning installation for work gangs," WO 94/21504 A1, filed Mar. 23, 1993, published Sep. 29, 1994.
Description: An optical (visual) warning installation for track work gangs.
§ 102 assessment: Relevant to the general problem of warning work gangs, and tangentially to the '792's visual display 34 alarm. It is wayside/optical, not RF, and lacks the train-operator alarm and confirmation loop. No anticipation of claims 1/7/8; marginal relevance to claim 4 (visual alarm).

Reference 11 — US 5,415,369 A (Rockwell International)

Full citation: Rockwell International Corp., "Railroad in-cab signaling with automatic train stop enforcement utilizing radio frequency digital transmissions," US 5,415,369 A, filed Sep. 29, 1993, issued May 16, 1995.
Description (as characterized in US 5,727,758's background): A train has an RF transceiver communicating with an RF transceiver at a railroad signal; digital RF in-cab signaling with automatic train stop enforcement.
§ 102 assessment: Highly relevant to two elements of the '792 claim set: (i) a train-carried RF transceiver (receiver and transmitter) and (ii) an in-cab alarm to the operator. But the counterpart station is a fixed wayside signal, not personnel; and there is no worker-carried device and no worker-directed confirmation alarm. The reference is strongly relevant as § 103 secondary art for the train-side transceiver/alarm elements; it does not anticipate the independent claims.

Reference 12 — US 5,461,366 A (CORIS)

Full citation: Compagnie d'Etudes, de Réalisations et d'Installations de Systèmes (CORIS), "Remote alarm system," US 5,461,366 A, filed Jun. 9, 1993, issued Oct. 24, 1995.
Description: A remote alarm system (generic remote alarm/telemetry).
§ 102 assessment: Generic alarm-communication art; no railway-worker or train-operator topology, no confirmation loop. No anticipation; at most background on remote alarm annunciation.

Reference 13 — US 5,554,982 A (Hughes Aircraft / Shirkey et al.)

Full citation: Keith L. Shirkey & Bruce A. Casella, "Wireless train proximity alert system," US 5,554,982 A, filed Aug. 1, 1994, issued Sep. 10, 1996 (Assignee: Hughes Aircraft Co.).
Description (from full text): A train-mounted transceiver (VPAS 22) periodically transmits the train's coordinates and speed; a crossing-based transceiver (WAVS 36) computes time-to-arrival and, when the train is 20–30 seconds out, transmits crossing coordinates and a warning zone; a vehicle-based receiver (VPAS 54) compares positions/speeds and produces a blinking light (64) and beeper (66) alarm to the vehicle operator. The system includes a "handshake" signal (47) from WAVS to the train and warning-zone deactivation by Train Detection Device sensors. It expressly notes warning-time ranges (6–10 s lead; alarms >10 s "tend to be ignored") and speed/braking-dependent ranges.
§ 102 assessment: This is the most technically overlapping US reference on the timing/confirmation sub-aspects:

• Confirmation/handshake element (claim 1's train→station RF confirmation): US 5,554,982's "handshake" travels WAVS→train, i.e., opposite to the claimed train→personnel confirmation, and confirms that the wayside unit is working — not that the operator has acknowledged. Not anticipatory of the confirmation limitation.
• Speed/time-dependent alarm timing (claim 1/7/8's "predetermined amount of time"): the reference computes alarm timing from train speed and time-to-arrival, but the receiver computes it, whereas the '792 claim ties the time to the transmit power of the worker transmitter. Different mechanism.
• Alarm recipient: the '982 alarm is in the motor vehicle, not in the train operator's cab, and the system is a grade-crossing/motorist system — not a railroad-worker-warning system.

Conclusion: US 5,554,982 is strong § 103 combination art against the confirmation/timing concepts, but it does not disclose the full combination of claim 1 (no worker-carried transmitter, no train-operator alarm, no operator-acknowledgment return loop). No § 102 anticipation.

Reference 14 — US 5,572,201 A (Federal Signal Corp.)

Full citation: Federal Signal Corporation, "Alerting device and system for abnormal situations," US 5,572,201 A, filed Aug. 5, 1994, issued Nov. 5, 1996.
Description: An alerting device/system that annunciates abnormal situations (alarm annunciation circuitry, likely including radio-triggered alert receivers).
§ 102 assessment: Generic alerting art. It relates only to the alarm-generating function common to the '792 receiver claims (4–6) and is not anticipatory of any independent claim; no railway-worker/train topology or confirmation link.

Reference 15 — US 5,620,155 A (Michalek)

Full citation: Jan K. Michalek, "Railway train signalling system for remotely operating warning devices at crossings and for receiving warning device operational information," US 5,620,155 A, filed Mar. 23, 1995, issued Apr. 15, 1997.
Description (from full text): A GPS-based locomotive system: the locomotive signals its approach to upcoming grade crossings to activate lights/bells/gates; each crossing performs self-diagnostic checks and relays data back to the locomotive (a two-way link, the locomotive being the receiver of crossing status); the system can signal approach directly to specially equipped motor vehicles (dashboard visual/aural alerts), and a locomotive can signal its position to other locomotives for collision avoidance.
§ 102 assessment: Two-way train↔wayside communication is present, but the "return" leg carries crossing-diagnostic/ID data to the locomotive — the inverse of the '792's operator-acknowledgment-to-personnel confirmation. The alarm recipients are motorists / other locomotives, not track personnel, and there is no worker-carried transmitter. No anticipation of claims 1/7/8; useful as § 103 art for the general two-way RF train signaling concept.

Reference 16 — US 5,727,758 A (Penza) — the closest prior art

Full citation: George Gregory Penza, "Tactile and audible warning system for railroad workers," US 5,727,758 A, filed Mar. 26, 1997, issued Mar. 17, 1998 (same inventor family as the '792).
Description (from full text): A train-mounted transmitter 20 continuously transmits an RF warning signal (900–980 MHz, variable power output); workers carry portable pagers 24 with an RF receiver 26 that actuates visual (32), audio (36), and vibratory (40) alarms. An optional control base 42 with transceiver 48 (receiver 50 + transmitter 52) receives the train signal, sounds a base alarm (visual 56 / audio 60), and retransmits to the pagers to overcome obstructions. Encoder/decoder coding is discussed for interference immunity.
§ 102 assessment: US 5,727,758 is the reference expressly acknowledged and distinguished in the '792 specification ("a problem with the warning system and method disclosed in the U.S. Pat. No. 5,727,758 patent is that while the personnel are aware of the presence of the approaching train, the train operator may be unaware of the presence of the personnel"). It discloses:

• the worker warning (train→worker) — the reverse of the '792's worker→train warning;
• portable receiver + visual/audio/vibratory alarms (in the worker pager, not in the train cab);
• a control base alarming all personnel.

It does not disclose (i) a worker-carried transmitter that warns the train operator, (ii) a train-operator alarm, or (iii) the train→personnel RF confirmation/alarm loop. Because anticipation requires a single reference to disclose every limitation, US 5,727,758 cannot anticipate claim 1, 7, or 8 — it is missing at least the confirmation-signal and train-operator-alarm limitations. It is the primary § 103 starting reference and the natural § 102 backdrop.

Companion reference not in the "Citations" list: US 5,924,651 A (Penza, filed 1998-03-17, issued 1999-07-20), a continuation-in-part of US 5,727,758, appears among the "Similar Documents." Its flow diagram expressly recites "transmitting a warning signal at a given power output from an approaching incoming train… providing a speed signal indicative of the speed of the train… controlling the power output of the warning signal as a function of the speed signal." This speed-dependent power control is materially closer to the '792 claims' "given power output… dependent upon the speed of the train" than any reference actually listed in the '792 Citations section, and — being a US patent granted on an application filed before 1998-04-29 — is a potential § 102(e) reference. I flag it because the examiner's citation list omits it while citing its parent; this is worth verifying against the file history if a validity opinion is being prepared.

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3. Mapping: which references could anticipate which claims

Key legal frame: Anticipation under § 102 requires one reference to disclose every element, arranged as in the claim. The '792 independent claims (1, 7, 8) require all of: (a) worker/personnel-side transmitter; (b) train-side receiver with operator alarm; (c) speed/power-dependent predetermined warning time; (d) train-side confirmation transmitter; (e) personnel-side confirmation receiver + alarm. No reference in the citation list discloses elements (a), (d), and (e) together with (b)/(c). Consequently:

Bottom line on § 102: On the record retrieved, no one of the 16 cited references appears to anticipate any claim of US 6,145,792, because each independent claim's confirmation-loop (train→personnel acknowledgment) and/or worker-transmitted warning to the operator is absent from every cited reference. The strongest candidate — US 5,727,758 (the inventors' own earlier patent, expressly distinguished in the specification) — discloses the mirror-image system (train→worker warning) and therefore cannot anticipate.

§ 103 exposure (for completeness, not asked but material): The claimed subject matter is most plausibly attacked as an obvious combination of:

• US 5,727,758 (worker paging/alarms, control base) + US 5,415,369 or US 5,620,155 (train-side transceiver, two-way train/wayside RF) for the confirmation back-channel; and
• US 5,554,982 for speed/time-to-arrival-dependent warning timing; and
• US 5,924,651 for speed-dependent power control (if it qualifies as prior art).

The "personnel-worn transmitter warns the train, which confirms receipt back to the personnel" reversal is the feature most likely to carry patentability, which is consistent with the patent having issued.

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4. Forward citations (context, not prior art)

The '792 is cited by numerous later worker-protection systems (e.g., the Metrom Rail worker-protection family, Harsco work-block-encroachment systems, Bombardier/Siemens track-worker safety systems, and the 2015+ Miller Felpax roadway worker systems). These are descendants, not prior art to the '792, and are relevant only as evidence of the field's subsequent development. I note them for completeness because the databases list 36 (front page) / 80 (expanded) citing documents.

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5. Confidence and limitations

• High confidence: bibliographic data for US 6,145,792 (number, application 09/069,132, filing 1998-04-29, grant 2000-11-14, inventors Penza, status Expired–Lifetime) and the full text of US 5,727,758, US 5,554,982, US 2,762,913, US 5,620,155, and JP H04-126664 (as characterized in US 5,727,758's background).
• Moderate confidence: US 5,415,369, US 5,303,259, US 5,461,366, US 5,572,201, DE 2,405,408, DE 4,219,067, WO 94/21504 (title/abstract-level only).
• Low confidence / not substantiated: JP S63-315369, JP H04-163273, JP H06-1239 — I retrieved only titles; I did not obtain machine translations, so I expressly decline to assert § 102 anticipation for these three. Any validity opinion should obtain the JP full texts and certified translations.
• I did not directly query uspto.gov PatentCenter; the USPTO "database" results reflected in this analysis came through Google Patents/Justia/third-party mirrors. If a formal USPTO record (e.g., PatentCenter or the IFW/file wrapper) is needed, that should be pulled separately, particularly to confirm whether US 5,924,651 was actually considered during prosecution (it is conspicuously absent from the front-page Citations list despite being the parent's CIP).

I'll analyze the obviousness of US6145792 under § 103 using the prior art cited on the patent page. Let me first research the key references.

Let me research more of the key prior art references.

Let me research the remaining references relevant to the bidirectional/portable aspects.

I've reached my research limit, but I retrieved enough detail on the key references. Below is my analysis. Where I could not verify the full content of a reference (only its title/abstract), I say so explicitly rather than overstate.

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Obviousness Analysis of U.S. Patent 6,145,792 (the "'792 patent") under 35 U.S.C. § 103

Identification note (literal IDs preserved): the patent is US6145792A, application US09/069,132, filed 1998-04-29, granted 2000-11-14, "Railroad worker warning system for train conductors," inventors George Gregory Penza and George Robert Penza. Because the application was filed before 2013, the pre-AIA version of §103 governs.

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1. Legal framework and level of ordinary skill

Framework. Under Graham v. John Deere Co., 383 U.S. 1 (1966), obviousness turns on: (1) the scope and content of the prior art; (2) the differences between the prior art and the claims; (3) the level of ordinary skill; and (4) objective indicia (secondary considerations). Under KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007), a combination of known elements is obvious where it does no more than yield predictable results, and an express teaching, suggestion, or motivation is not required — a reasoned articulation suffices (plus, where relevant, "obvious to try," design incentives, and market/safety demands).

Level of ordinary skill (PHOSITA). A person of ordinary skill would have a bachelor's degree in electrical/communications engineering (or equivalent), with roughly 2–4 years of experience in RF/paging and railroad signaling or wayside-worker warning systems, and would be familiar with the "tactile and audible warning system" of the applicants' own earlier work and with conventional in-cab signaling. (This is my reasoned estimate; the patent is silent on the level of skill.)

Prior-art dates relevant to §102(b) (critical date 1997-04-29, one year before filing). The following cited references predate the critical date by more than one year and thus are §102(b) art: US2762913A (1956), DE2405408A1 (1975), JPS5235504A (1977), JPS63315369A (1988), JPH04126664A (1992), JPH04163273A (1992), DE4219067A1 (1993), JPH061239A (1994), US5303259A (1994), WO1994021504A1 (1994), US5415369A (1995), US5461366A (1995), US5554982A (1996), US5572201A (1996), US5620155A (1997-04-15).

Important caveat on US5727758A. The citation list includes US5727758A ("Tactile and audible warning system for railroad workers," Penza), which issued 1998-03-17 — within one year of the '792 filing date — and therefore is not §102(b) art standing alone. It also shares inventorship with the '792 patent (same inventive entity), which raises a question whether it is "by another" under §102(a)/(e). However, the '792 specification itself expressly acknowledges US5727758A as the applicants' prior invention and uses it as the admitted starting point ("A problem with the warning system and method disclosed in the U.S. Pat. No. 5,727,758 patent is that while the personnel are aware of the presence of the approaching train, the train operator may be unaware of the presence of the personnel"). It is therefore properly treated as admitted prior art/background. The companion US5924651 appears only in the "Similar Documents" list (a later-issuing continuation-in-part of '758) and is not relied on as prior art.

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2. The claimed subject matter

Independent claim 1 (system) requires:

• (1a) a transmitter adjacent the personnel transmitting an RF warning signal with a given power output along a wireless RF path;
• (1b) the power output dependent upon the speed of the train;
• (1c) the signal indicative of the presence of personnel;
• (1d) a receiver on the train receiving the signal;
• (1e) receipt a predetermined amount of time before the train reaches the personnel, that time being dependent on the power output;
• (1f) the train receiver generates an alarm to notify the train operator;
• (1g) a transmitter on the train sending an RF confirmation signal upon receipt;
• (1h) a receiver adjacent the personnel receiving the confirmation; and
• (1i) that receiver generates an alarm to notify the personnel that the operator is aware of their presence.

Claim 7 is the same system with a portable transmitter and portable receiver "carried by at least one of the personnel." Claim 8 is the method counterpart of claim 1 (plus a confirmation-signal step). Claims 2–3 and 9–10 add the portable form factor; claims 4, 5, 6 add visual, audio, and vibratory alarms, respectively.

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3. Scope and content of the cited prior art

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4. Element-by-element comparison and the differences

Net difference over the closest admitted art (US5727758A): (i) inversion of the warning direction — personnel/wayside now transmits to the train so the operator is warned; and (ii) a return confirmation signal from the train to the personnel indicating the operator is aware.

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5. Grounds of rejection under §103

Ground A (primary): US5727758A in view of US5415369A; further in view of US5554982A

Rationale. US5727758A supplies everything on the personnel side and the alarm architecture: RF warning transmission at a given/variable power output, a portable receiver carried by personnel, and visual, audio, and vibratory alarms (claims 4–6), plus a station transceiver. US5727758A, however, "only" warns the personnel. US5415369A expressly identifies that limitation of the art — that prior systems "only provide information to the approaching locomotive" and "do not typically provide a means for the transfer of information from the locomotive to other railroad entities" — and teaches the remedy: a locomotive RF transceiver that both receives wayside information (displayed to the engineer) and transmits data back to the wayside. US5554982A supplies the speed-dependent warning timing and the handshake/confirmation concept (a signal sent to confirm the counterpart is functioning/aware).

Motivation to combine. The '792 specification itself frames the problem: with US5727758A, "the personnel are aware of the presence of the approaching train, [but] the train operator may be unaware of the presence of the personnel." A POSITA addressing worker safety would (a) add a train-bound warning so the operator can take corrective action, and (b) add a return confirmation so the workers know the operator has received the warning — closing the communication loop, mirroring the acknowledged-acknowledgment practice in railroad signaling (e.g., ATS acknowledgment in US5415369A) and the flagperson/lookout practice described in the '758 background. All elements are known and combine to yield only predictable results (KSR).

Ground B: US5727758A in view of US5620155A (and/or US5554982A)

Rationale/motivation. US5620155A teaches that a locomotive transmits to wayside equipment (to activate crossing warning devices) and that wayside equipment relays information back to the locomotive, and additionally uses GPS speed/position data. Combining with US5727758A yields a two-way train↔wayside RF system in which the wayside/personnel side can both transmit a warning toward the train and receive/act on a confirming response, and in which timing can be made speed-dependent — squarely meeting claims 1/7/8. The motivation is the same recognized need for reciprocal communication between train and wayside personnel/equipment in a safety-critical environment.

Ground C (dependent claims): US5727758A alone or in the above combinations

Claims 2, 3, 9, 10 (portable transmitter/receiver "carried by at least one of the personnel"): met directly by the portable pager carried by personnel in US5727758A, and by the portable warning equipment of DE2405408A1. Claims 4, 5, 6 (visual, audio, vibratory alarms): met directly by US5727758A's visual display 32, audio alarm 36, and vibrative alarm 40. These dependent claims add nothing beyond the admitted art and would fall with the independent claims.

Ground D (secondary/alternative): reversal of parts

A further, independent line of reasoning is the "reversal of parts" doctrine: US5727758A already places a transmitter on one platform and a receiver (with an alarm) on the other, and already includes a station transceiver (48) with both a receiver 50 and a transmitter 52. Simply swapping which platform transmits and which receives, to warn the operator instead of the workers, produces no new or unexpected result — it merely redirects an existing warning. That, standing alone, is strong evidence of obviousness for the direction-inversion element.

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6. Motivation-to-combine synthesis (why a POSITA would combine)

1. Same field, same problem. Every reference is directed to railroad worker/operator safety and RF-based warning (US5727758A, US5415369A, US5620155A, US5554982A, US2762913A, JPH04126664A). The '792 patent itself classifies in B61L23/06 ("warning men working on the route").
2. Recognized deficiency and its known cure. The '792 background states the exact deficiency of US5727758A (operator unaware), and US5415369A/US5620155A supply the known cure (train↔wayside two-way RF).
3. Predictable results / no unexpected mechanism. Each claim element (RF transmitter/receiver, alarm, power control by speed, confirmation signal) is a known component performing its known function; the combination yields the expected benefit of reciprocal awareness with a reasonable expectation of success.
4. Safety and cost incentives. Warning the operator a predetermined time (e.g., ≥15 seconds) ahead, and confirming acknowledgment, reduces the need for lookouts/flagpersons described in the '758 background — a market/incentive motivation recognized in KSR.

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7. Weaknesses of the §103 case / possible non-obviousness positions

To be balanced (the patent did, after all, issue over these references):

• No single reference discloses the full combination (personnel-side transmitter + train-side alarm + train-side confirmation transmitter + personnel-side confirmation alarm). The case is a true multi-reference combination.
• Direction specificity. The cited art's two-way railroad links (US5415369A, US5620155A) are train↔wayside-signal/equipment links, not train↔worker-carried links; a patent owner could argue that the worker-carried confirmation alarm (1i) is not squarely taught, and that US5554982A's "handshake" runs the opposite direction (wayside→train).
• Reference availability. US5727758A is the applicants' own prior patent and is within one year of filing; its status as "prior art by another" under §102(a)/(e) is questionable (see §1). If US5727758A is excluded as prior art, the speed-dependent-power/portable-alarm teachings would need to be sourced from other cited references, several of which I could verify only at the title/abstract level (DE2405408A1, US5461366A, US5572201A, JPH04126664A, JPH04163273A, JPH061239A, JPS5235504A, JPS63315369A, WO1994021504A1). I do not have high-confidence full-text knowledge of those references and would not assert them as complete anticipations without further verification.
• Timing nuance. In the '792 claims, the personnel-side transmitter's power output is "dependent upon the speed of the train," yet the personnel side does not directly sense train speed; the specification resolves this by assuming maximum allowable train speed. A patent owner could argue that the cited speed-dependent-power art (train-side control) does not render obvious a wayside-set, speed-assumption-based power selection.

These points could support a non-obviousness argument, but they are vulnerabilities of application, not clear teachings away — and under KSR a reasoned articulation of the above combinations would likely be sufficient to make a prima facie case.

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8. Conclusions

• Independent claims 1, 7, and 8 would be prima facie obvious under §103 over US5727758A in view of US5415369A, further in view of US5554982A (and/or US5620155A), because each limitation is disclosed by these references and the combination merely closes a communication loop that the '792 specification itself identifies as desirable, yielding predictable results.
• Dependent claims 2–6, 9, 10 would likewise be obvious, as the portable form factor and the visual/audio/vibratory alarm types are expressly disclosed in US5727758A (pager 24; display 32, audio 36, vibratory 40).
• The strongest single-recognition feature is the combination of (i) inverting the warning direction so the operator is warned and (ii) adding a train→personnel confirmation alarm; the reversal-of-parts doctrine and the analogous "handshake"/acknowledgment teachings (US5415369A, US5620155A, US5554982A, US2762913A) support finding this combination obvious.
• Confidence caveats (stated explicitly): I have full-text confidence for US5727758A, US5415369A, US5620155A, US5554982A, US2762913A, and the '792 specification; for DE2405408A1, US5461366A, US5572201A, JPH04126664A, JPH04163273A, JPH061239A, JPS5235504A, JPS63315369A, DE4219067A1, and WO1994021504A1 I relied on the titles/abstracts shown on the patent page and should verify full text before relying on them as anticipatory. No objective indicia (secondary considerations) appear anywhere on the '792 record, and the patent is now "Expired – Lifetime" (anticipated expiration 2018-04-29), so the practical stakes are historical.

Citation anchors: all quoted reference language is drawn from the Google Patents page for US6145792A (https://patents.google.com/patent/US6145792/en) and from the corresponding reference pages (US5727758A, US5415369A, US5620155A, US5554982A, US2762913A) retrieved during this analysis.