US 5620155

I'll search for authoritative information on this patent number and any 2026 CAFC docket activity.

Let me check specifically for any current litigation or CAFC activity, and confirm the legal status.

US Patent 5,620,155 — Analyst Summary

Search scope note: I queried for patent 5,620,155 specifically (not similar numbers). The authoritative full text supplied in-session (Google Patents, fetched 2026-09-24) plus corroborating sources — uspto.report, Justia Patents, USPTO PTAB/PTACTS records — are the basis for the bibliographic data below. I found no CAFC docket and no PTAB proceeding naming 5,620,155 as the patent-in-suit or patent at issue in 2026 (or any year). Every 2026-era PTAB/CAFC hit for the string "5620155" is a prior-art citation (e.g., Ex. 1010, "Michalek") in IPRs involving later, different patents — notably the Metrom Rail IPRs (U.S. 9,043,131 / related) and Quantum Engineering/Byers-family challenges. Absence of a 2026 CAFC docket is an inference from my searches, not a certified negative; treat it as reported, not proven.

Bibliographic Data

Caution on assignee/ownership: A "Jan Michalek" appears in unrelated records tied to Estech, LLC (a solid-waste-processing patent), and a search hit flagged Jan K. Michalek (Pataskala, OH). I have no authoritative evidence linking that entity or individual to ownership of 5,620,155. Per the patent record, ownership remained with an individual, and the patent lapsed in 2005. Any current ownership/chain-of-title claim would be speculation.

Abstract (as issued)

A signalling system for a railroad locomotive that lets the locomotive signal its approach to upcoming railroad crossing signals so the crossing activates lights, bells, or similar warning devices. A GPS receiver on the locomotive determines train location (and thus proximity to known crossing locations). The crossing includes a self-diagnostic mechanism checking internal conditions (e.g., low battery, burned-out bulb), and that diagnostic information, together with a digitally encoded crossing identification, is relayed to the locomotive as it passes. Maintenance information for every so-equipped crossing is thereby collected on the locomotive for later interrogation at service locations. The system also can signal approaching locomotives directly to specially equipped motor vehicles, and to other locomotives for collision avoidance if a train becomes disabled.

Plain-Language Overview of the Independent Claim

Claim 1 (the sole independent claim) recites a railroad signalling system with four required elements:

1. (a) Train-side first transmitter — transmits first electromagnetic signals from the train sequentially to multiple crossing warning devices along the route. Those signals carry (i) digitally encoded identification specifying each crossing and (ii) digitally encoded control instructions controlling the function of the crossing warning devices.
2. (b) Crossing-side second transmitter — at each crossing, transmits second signals back to the train, carrying (i) digitally encoded identification of that crossing and (ii) digitally encoded information about the operational condition of the crossing warning devices.
3. (c) Train-side first receiver + memory — receives those second signals and stores them.
4. (d) Crossing-side second receiver — compares the received crossing-identification code against an internally stored predetermined identity code, and controls the crossing warning devices in response to the received control instructions only when the transmitted identity code matches the stored code.

Practical meaning: The train both commands and interrogates crossings, using per-crossing digital addressing so only the intended crossing responds; the crossing reports back its own ID and health status, which the train logs.

Dependent Claims (plain language)

• Claim 2 — Adds a means for locating the geographical position of the train's transmitter.
• Claim 3 — Specifies the locating means is a global satellite positioning (GPS) system: an on-board GPS receiver plus processing to derive geographic location.
• Claim 4 — Train transmits "turn on" instructions when its location is within a predetermined distance of the crossing's location.
• Claim 5 — Stores the train length in the train-side equipment.
• Claim 6 — Train transmits "turn off" instructions once the end of the train (using train length) has passed the crossing by a predetermined distance.
• Claim 7 — Train transmits its geographic location to receivers on other trains (collision-avoidance positioning).
• Claim 8 — Adds a battery power source for the crossing transmitter and receiver.
• Claim 9 — Adds solar electrical generating means to recharge the crossing batteries.
• Claim 10 — Depends from claim 1 and adds motor-vehicle signalling (dashed numbering a′–c′ in the original): the train's signals further carry a third, distinct digital identity code for motor vehicles plus motor-vehicle control instructions; a third receiver in the vehicle matches its stored code and actuates the vehicle's warning devices.
• Claim 11 — Adds retrieval of the stored second signals to determine the identity and operational condition of the crossing warning devices (maintenance readout function).

Key Uncertainty Flags

• No litigation/appeal found: I could not identify any CAFC 2026 docket, district-court case, or PTAB proceeding in which 5,620,155 is itself the patent-at-issue. Its only modern appearance is as prior art in third-party IPRs (Metrom Rail and Quantum/Byers-related challenges). These are current as of my searches (which surfaced 2026 CAFC and PTAB filings).
• Enforceability is moot: The patent lapsed in 2005 for non-payment of maintenance fees, well before its 2015 anticipated expiration. It cannot be asserted today.
• Assignee ambiguity: Recorded assignee is an individual. I found no reliable documentation of any assignment to a company; the "Estech" association in search results concerns a different Michalek patent (waste processing) and should not be attributed to 5,620,155 without a recorded assignment instrument.

I'll search for litigation involving US patent 5620155.

Let me search more targeted litigation databases and terms.

Summary of Findings

No litigation involving U.S. Patent No. 5,620,155 is known. My searches of litigation-oriented sources (Unified Patents litigation/PTAB portals, CourtListener/RECAP dockets, PACER-sourced material, Justia patent pages, and general web) returned no district court case, no Federal Circuit appeal, and no PTAB proceeding (IPR/PGR/CBM) in which U.S. Patent 5,620,155 was asserted, challenged, or otherwise at issue.

What the searches actually returned (and why it is not litigation)

None of these constitutes litigation over U.S. Patent 5,620,155.

Corroborating context from the patent record

U.S. Patent 5,620,155 (Michalek, "Railway train signalling system for remotely operating warning devices at crossings and for receiving warning device operational information," filed 1995-03-23, granted 1997-04-15) shows the following USPTO legal-events history:

• 2000-11-07 — maintenance-fee reminder mailed
• 2001-03-23 — 4-year fee paid (with surcharge for late payment)
• 2004-11-03 — maintenance-fee reminder mailed
• 2005-04-15 — lapse for failure to pay maintenance fees
• 2005-05-18 / 2005-06-14 — patent expired due to nonpayment of maintenance fees under 37 CFR 1.362, effective 2005-04-15
• Current status: Expired – Fee Related
• Assignee: Individual (never assigned to a large operating company or an NPE)

A patent that lapsed in 2005 and was never assigned to an asserting entity is highly unlikely to have been the subject of infringement litigation, which is consistent with what the searches found.

Important caveats

1. Search coverage is not exhaustive. Free sources (Unified Patents portal, CourtListener/RECAP, Justia, Google) do not perfectly index every state-court filing, every old pre-2000s district court case, or every sealed/terminated matter. Paid services (Lex Machina, Darts-IP, Westlaw/Lexis litigation modules, Bloomberg Law) would provide more definitive negative-clearance.
2. I found no Federal Circuit decision mentioning this patent, and no result tying the patent to any named plaintiff or defendant.
3. I did not locate any entry on the Unified Patents case list (https://portal.unifiedpatents.com/litigation/caselist) for 5,620,155. I could not directly open that portal during this session, so this is based on indexed references to it rather than a direct portal query.

Bottom line

Based on all available public sources, there is no known litigation involving U.S. Patent No. 5,620,155. The only appearances of the number "5620155" in patent-related materials are as (a) a cited prior-art reference in the prosecution of other patents (e.g., the Quantum Engineering/Kane family) and (b) a search-string entry in PTAB petitions concerning unrelated patents. The patent expired in 2005 for failure to pay maintenance fees and was held by an individual inventor, with no recorded assertion activity.

If you need a definitive litigation-clearance opinion, I recommend running the number through Lex Machina, Darts-IP, or a PACER full-text search (5:620,155 / 5620155) rather than relying solely on the free sources above.

I'll start by verifying the structured "no proceedings" signal against web sources, since the ODP block is authoritative for the canonical list but may lag.

The direct searches return only prior-art citations to the '155 patent, not proceedings against it. Let me run a few more targeted checks to be thorough.

Let me confirm there's no AIA proceeding and check for any reexamination or litigation involving the '155 patent itself.

I was unable to complete additional verification searches (tool step limit reached), but the searches completed before that point — plus the authoritative structured block — are consistent. Here is the analysis.

Proceedings overview

Total AIA trial proceedings on file for US 5,620,155: 0 (0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denied). The USPTO ODP structured feed reports no AIA trial proceedings, and my independent web checks surfaced no IPR/PGR/CBM against this patent — the only appearances of "5,620,155 / 5620155" in Board materials are as prior art (Michalek) cited against other patents, not as the challenged patent. Bottom line for a defendant: this is not a "hardened survivor of IPR" story — it is a zero-PTAB-activity story complicated by the fact that the patent lapsed on 2005-04-15 for failure to pay maintenance fees and lapsed again into "Expired – Fee Related" status. If you are being asserted on the '155 patent today, the threshold issue is not claim validity but whether an expired, fee-lapsed patent can support the demand at all.

No AIA trial proceedings to itemize

Because the canonical list is empty, there are no {PROCEEDING_NUMBER} sections to write, and I will not invent any. For completeness, the closest thing to PTAB "activity" involving this patent is that others' IPRs cite it as prior art:

• IPR2017-02044 (Petitioner v. Siemens, owner of U.S. 6,609,049) — the Board's institution decision relied on ground 4, "claims 8 and 18 under 35 U.S.C. § 103 as unpatentable over Byers and Michalek," where "Michalek" is U.S. Patent No. 5,620,155 (Ex. 1010). The panel found a POSITA "would have both readily combined the teachings of Byers and Michalek." (institution decision mirror; petition materials).
• Similar petitions against the '461 and '774 patents likewise cite Michalek (Ex. 1010, cited by the examiner) as prior art.

None of these proceedings challenged the '155 patent itself, so they neither cancel nor sustain any claim of it. I found no record of any ex parte or inter partes reexamination, and no district-court assertion, in the sources I was able to search — I flag that as a gap in my verification, not a confirmed negative, since I could not run the full set of confirmatory searches.

Status nuance (from the authoritative record): the structured data lists the patent as Expired - Fee Related, with legal events LAPS – Lapse for failure to pay maintenance fees (2005-04-15), STCH – PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 (2005-05-18), and FP – Expired due to failure to pay maintenance fee (effective 2005-04-15). The "anticipated expiration 2015-03-23" entry reflects the 20-year nominal term; the patent actually died in 2005 for nonpayment. (Google Patents US5620155)

Strategic summary

Claim status — CANCELED vs. SUSTAINED vs. UNTESTED. No claim of US 5,620,155 has ever been canceled or sustained by the PTAB, because no claim was ever challenged in an AIA trial. On paper, claims 1–11 are all UNTESTED at the Board. That is not a defensive win for the patent owner in any meaningful sense: with the patent lapsed for nonpayment in 2005, the claims carry no enforceable term, and the "untested" label reflects that nobody had an economic reason to attack a dead patent rather than that the claims were validated. For a defendant, treat any current assertion resting on claims 1–11 as facing an immediate standing/enforceability problem (expired, fee-lapsed patent), independent of § 102/§ 103 merits.

Estoppel landscape. There is no § 315(e)(2) estoppel to worry about — estoppel only attaches to a petitioner (and privies) after a final written decision in that petitioner's IPR, and no IPR exists here. Accordingly, every prior-art ground remains available to a defendant, including the very art the Office itself later used: Byers+t (as in IPR2017-02044's ground 4), plus the references the examiner cited against the '155 patent during prosecution — e.g., US 3,758,775 (Dept. of Transportation), US 4,104,805 (Gibson), US 4,934,633 (Harmon "Crossing control unit"), US 4,942,395 (Ferrari), and the Japanese references JPH0260881A and JPH0455163A. None of that art is foreclosed by estoppel.

Pattern signals. No pattern to read — there is no petitioner to have filed multiple IPRs, no patent-owner PTAB appeal history, and no sign of a defensive-aggregator (e.g., Unified Patents) campaign against the '155 patent. The patent's modern relevance is essentially bibliographic: it functions as prior art that later railroad-signaling patents must design around. Note also the chain of later patents that cite the '155 patent (e.g., the Siemens/Quantum horn-activation family around the '049 patent), which is where the real PTAB action has occurred.

Recommended next steps

• No PTAB activity exists here — say so plainly. The absence is itself the signal: a patent that could support a licensing or assertion program would, by now, have attracted an IPR. This one has not, and its expiration for nonpayment in 2005 is the reason. I could not fully rule out an old district-court or reexamination record within my search budget, so a defendant should confirm the litigation/reexam history via PatentCenter and PACER before finalizing any strategy memo.
• Lead with the lapsed status, not validity. The defensible, citable fact is the 2005 maintenance-fee lapse and Expired - Fee Related status (Google Patents US5620155). If a demand letter cites claims 1–11, the first response is that the patent term ended in 2005 for nonpayment — infringement theory on an expired patent is not viable, and this issue is prior to and dispositive of any § 102/§ 103 fight.
• If (and only if) you nonetheless need invalidity positions, remember there is no estoppel: you are free to use any ground, and the '155 patent's own prosecution citations plus the Byers+Michalek combination popularized in IPR2017-02044 give you a starting set of references — but confirm whether § 315(b)'s one-year bar or any estoppel applies to you from your own prior proceedings, since the patent owner's own record is silent on that.

Confidence and limitations: High confidence that no AIA trial proceeding appears in the canonical ODP data or in the Board materials I retrieved. Moderate confidence that no reexamination or litigation exists, since I could not complete the full set of confirmatory searches before hitting the tool limit — I have flagged this rather than assert a negative I did not fully verify.

I'll verify the assignment record and cross-reference sources before drafting.

Inventors

Notes / unusual patterns:

• This is a single-inventor, individually-owned patent. In the mid-1990s radio/GPS train-signalling field, filings of this type were overwhelmingly corporate (e.g., Harmon Industries, WABCO/Westinghouse Air Brake, Union Switch & Signal). An all-Individual record is atypical and usually indicates an independent inventor or an academic rather than an R&D-organization filing.
• No departure pattern is observable — with a single inventor and no corporate assignor, there is no "inventor leaves the assignee" event to measure.
• Public-records aggregators associate a "Jan K. Michalek" with Pataskala/Newark, Ohio, and co-inventorship on unrelated solid-materials processing patents (e.g., with Theodore J. Thomas, Columbus, OH). This is a name match only, not a verified identification, and I could not confirm it connects to US 5,620,155. Treat the employer as unknown.
• The patent's claims are heavily cited as prior art in later IPRs on train-horn / locomotive database systems (e.g., references to "Michalek" in PTAB filings concerning US 7,721,134-era horn-activation art), confirming its technical relevance — but that is citation activity, not assertion activity by the owner.

Original assignee

• Original assignee of record: Individual (the inventor, Jan K. Michalek). There is no company on the issued patent.
• Product embodying the claims: None identified. No commercial product, no licensee, and no evidence the claimed locomotive-to-crossing signalling system was ever manufactured or sold by an assignee.
• Primary line of business: Not applicable — an individual, not a business entity.
• Current status: The patent is Expired – Fee Related. It lapsed 2005-04-15 for failure to pay maintenance fees, with formal expiration recorded 2005-06-14 ("PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362"). The rights did not survive to be monetized by any later owner.

Assignment timeline

The USPTO Assignment Center has no recorded assignment for US 5,620,155. I searched the Assignment Center (https://assignmentcenter.uspto.gov/ and the mirrored search at https://assignment.uspto.gov/patent/index.html) for patent number 5620155 / application 08/409,142 and found no reel/frame entries — no inventor-to-company assignment, no security agreement, no merger, no change of name, and no transfer to a licensing entity at any point in the patent's life.

This is corroborated by the patent's own legal-events record (Google Patents, https://patents.google.com/patent/US5620155/en), which lists only maintenance-fee events, with zero assignment events:

Interpretation: The patent was owned by the individual inventor for its entire enforceable life and was allowed to lapse in 2005 rather than being assigned, licensed, or asserted. There is no ownership chain to reconstruct and — critically for the NPE analysis — no assignee, no correspondent of record, and no transfer events to evaluate.

Per the report specification, analysis stops here because the Assignment Center shows no records for this patent. For completeness against the framework's categories, the classification is Insufficient data — no recorded assignments exist beyond the original issuance to the individual inventor, and the patent expired fee-related in 2005 with no successor owner in interest.

I'll verify the patent and its cited prior art against live sources.

Let me pull details on the key cited references.

Let me verify the remaining cited references.

Prior-Art Analysis — US Patent 5,620,155

1. Confirmation of the Target Patent

Live sources confirm the record. I searched for the exact number 5620155 and no other (per the strict rule, I did not substitute or "correct" any identifier).

Grounding URLs: Google Patents https://patents.google.com/patent/US5620155/en; USPTO full-text PDF https://patentimages.storage.googleapis.com/b9/39/05/94a59445b45a9d/US5620155.pdf.

Important scoping note. The Google Patents/UPSTO record shows two different lists that are easily confused:

• "Patent Citations (11)" — the references cited against '155 (examiner-cited, marked *). These are the relevant prior art and are the subject of this memo.
• "Cited By (146)" — later patents that cite '155 (e.g., Ferrari '213, Blesener, Central Signal, Siemens). These are not prior art to '155; they are forward citations and are excluded.

I could not retrieve full text for the two Japanese references (JPH0260881A, JPH0455163A) from the sources available to me; their descriptions below are drawn from the titles/abstracts listed on the '155 face and are flagged as such rather than asserted as complete.

2. The 11 Cited References

R1 — US 3,758,775 A ⭐ (most structurally relevant to the crossing side)

• Full citation: Hopkins, J.B., Railroad crossing signalling system, US 3,758,775 A; assignee U.S. Department of Transportation.
• Dates: filed 1971-09-29; published 1973-09-11.
• Description: Microwave telemetry carries control information from a remote track-sensor location to a receiver at the crossing; the receiver enables an active motorist warning device. Emphasises low-duty-cycle pulse modulation so a self-contained battery at the crossing can run ~12 months unattended, and a fail-safe "no beam = warning" logic.
• Potentially anticipates: Claim 1(d) only in part — "second receiver located at each crossing… means for controlling said warning devices." It also bears on claim 8 (battery power source at the crossing). It does not disclose a train-borne transmitter, digital addressing of a specific crossing, or any train-bound diagnostic feedback, so it cannot anticipate claim 1 as a whole.
• Source: https://patents.google.com/patent/US3758775A/en

R2 — US 4,942,395 A ⭐⭐ (closest overall to '155)

• Full citation: Ferrari, J.S.; McFarland, D.S.; Sommers, Railroad grade crossing motorist warning system, US 4,942,395 A.
• Dates: filed 1987-08-24; published 1990-07-17.
• Description: Three-part wireless system: (i) a locomotive-mounted transceiver beacon transmits a distance-limited coded shortwave signal; (ii) a crossing "crossbuck" pole-mounted transceiver, which may be battery powered with solar photovoltaic trickle charging for passive crossings, is triggered by the locomotive and re-broadcasts/emits a coded signal; (iii) a vehicle-mounted microprocessor receiver that discriminates the coded signal and actuates visual/voice alerts. The locomotive also receives confirmation from the crossing.
• Potentially anticipates: This is the single most threatening reference and the one the '155 specification itself distinguishes (it names Ferrari-type art as failing to provide self-diagnostic/selective digital encoding). It maps onto:
  • Claim 8 (battery power at the crossing) and Claim 9 (solar recharging) — Ferrari expressly discloses the battery + photovoltaic crossing unit.
  • Claim 1(a) partially (coded signal from locomotive to crossing) and 1(d) (crossing receiver controlling warning devices).
  • Claim 10 partially — though note Ferrari's vehicle warning is relayed through the crossing, whereas claim 10 requires the vehicle receiver to receive the train's own "third" code directly from the first transmitter. That difference matters for anticipation.
• It does not disclose GPS location, train length, selective per-crossing digital prefixes addressed uniquely to one crossing, or the crossing-to-train operational-condition feedback of claim 1(b)/(c) — the features on which '155's novelty principally rests.
• Source: https://patentimages.storage.googleapis.com/09/00/1e/243f78f1787195/US4942395.pdf

R3 — US 4,934,633 A (crossing-side control electronics)

• Full citation: Ballinger, F.H.; Farnham, W.L.; Schneider, W.G.; Crossing control unit, US 4,934,633 A; assignee Harmon Industries, Inc.
• Dates: filed 1988-10-07; published 1990-06-19.
• Description: Essentially fail-safe solid-state crossing controller driving a pair of warning lamps alternately at ~55 pulses/minute; a 500 Hz "safe status" signal holds the lamps de-energised, a warning-rate signal flips them into flashing. Superimposes control tones on the single lamp supply lead.
• Potentially anticipates: Claim 1(d) (means at the crossing for controlling the warning devices) as a structural sub-combination; also relevant background to the "burned-out bulb / lamp status" checking of claim 1(b). It says nothing about train-borne transmitters, GPS, or crossing-to-train telemetry.
• Source: https://patents.google.com/patent/US4934633A/en

R4 — JPH 0260881 A (diagnostics)

• Full citation: Mitsubishi Electric Corp., Obstacle detector for railway crossing (Japanese unexamined publication JP H02-60881 A).
• Dates: filed 1988-08-26; published 1990-03-01.
• Description (from title/abstract only — full text not retrieved): A railway-crossing obstacle detector. It is cited for the crossing-resident sensing/diagnostic function.
• Potentially anticipates: Claim 1(b) in the narrow sense of crossing-local condition sensing reporting on the state of the crossing area; not the train-bound, digitally-encoded operational-condition telemetry of claim 1(b)/(c).

R5 — JPH 0455163 A (diagnostics)

• Full citation: Nippon Signal Co., Ltd., Crossing rod operational abnormality detecting device for crossing gate (JP H04-55163 A).
• Dates: filed 1990-06-22; published 1992-02-21.
• Description (from title/abstract only): Detects abnormal operation of the crossing gate/barrier rod — i.e., the crossing self-reports a fault in its own warning apparatus.
• Potentially anticipates: Directly relevant to claim 1(b) ("digitally encoded information relating the operational condition of said warning devices") and to claim 11 (retrieving stored second signals to determine identity and operational condition). This is the reference pair the examiner used against the self-diagnostic aspect. It does not, however, disclose transmitting that condition to a passing locomotive with a digitally-coded crossing ID.

R6 — US 3,784,970 A

• Full citation: Simpkin, W., Emergency warning system with range control, US 3,784,970 A.
• Dates: filed 1971-02-17; published 1974-01-08.
• Potentially anticipates: Claim 10 concept (warning a road vehicle of an approaching vehicle based on signal range and a coded/limited signal). Referenced in '155's own background as emergency-vehicle art.

R7 — US 3,997,868 A

• Full citation: Ribnick, G.D., Emergency vehicle warning system, US 3,997,868 A.
• Dates: filed 1973-02-20; published 1976-12-14.
• Potentially anticipates: Claim 10 (in-vehicle receiver actuated by a transmitted identification/control code). Also a background reference in '155.

R8 — US 4,704,610 A

• Full citation: Smith, M.R., Emergency vehicle warning and traffic control system, US 4,704,610 A.
• Dates: filed 1985-12-16; published 1987-11-03.
• Potentially anticipates: Claim 10 — vehicle-borne receiver alerted when the (emergency) transmitter's identity code matches a stored code; also intersection-device activation.

R9 — US 4,775,865 A

• Full citation: Emergency vehicle warning and traffic control system, US 4,775,865 A; assignee E-Lited Limited (a California limited partnership).
• Dates: filed 1985-12-16; published 1988-10-04.
• Potentially anticipates: Claim 10 — the companion to R8; code-selective activation of roadside warning devices and in-vehicle alerts.

R10 — US 4,108,405 A

• Full citation: Gibson, P.H., Light assembly and flasher circuit, US 4,108,405 A.
• Dates: filed 1977-06-22; published 1978-08-22.
• Potentially anticipates: Claim 1(d) at the level of the warning-device driver (flasher circuit) only. Purely a hardware sub-combination.

R11 — US 5,429,329 A (temporal edge-case reference)

• Full citation: Wallace, C.C., Robotic railroad accident prevention vehicle and associated system elements, US 5,429,329 A.
• Dates: filed 1994-01-31; published 1995-07-04.
• Potentially anticipates: Claims 2–4 (determining/acting on the location of a rail vehicle relative to a crossing) and possibly claim 7 (broadcasting position for collision avoidance). ⚠️ Timing caveat: R11 published after the '155 filing date (1995-03-23), so it is not §102(a)/(b) art on its face. It could only be prior art under pre-AIA §102(e) as a US patent granted on an application filed (1994-01-31) before '155's filing/reduction to practice, assuming '155 is not entitled to an earlier date. Because '155's only priority date is its 1995-03-23 filing, §102(e) is available — but this should be verified against the examiner's stated basis, which the Google Patents record does not show.

3. Bottom Line

• No single cited reference anticipates claim 1 as a whole. Claim 1 requires the combination of (a) a train-borne transmitter sending per-crossing digitally coded identity + control to a plurality of crossings, (b) a crossing-borne transmitter returning crossing identity + digitally coded operational-condition data, (c) a train-borne receiver with memory storing that data, and (d) a crossing receiver that compares the received identity to a stored internal code before actuating the warning devices. R2 (Ferrari '395) supplies much of (a)/(d) and the battery/solar power at the crossing; R3 and R10 supply the warning-driver hardware; R5 and R4 supply crossing self-diagnosis. Every element is scattered across references — the case is an obviousness (§103) case, not a §102 anticipation case, on the face of the record.
• Strongest §102 candidates (each still short of a full claim): R2 (US 4,942,395) against claims 8 and 9 (battery + solar crossing unit) and, more weakly, claim 1(d); R5 (JPH 0455163) against the diagnostic concept in claims 1(b) and 11; R11 (US 5,429,329) against claims 2–4, subject to the §102(e) timing caveat above.
• Key distinguishing features not found in any cited reference: (i) GPS-based train position used to trigger only the designated upcoming crossing, (ii) per-crossing unique digital prefix addressing so that only the addressed crossing activates, (iii) storage of train length to compute a "turn-off" (claims 5–6), and (iv) storage of the crossing's returned diagnostic data aboard the locomotive for later retrieval (claims 1(c), 11). These are the features the '155 specification itself uses to distinguish the emergency-vehicle art of R6–R9.

Caveats / confidence: Patent number, dates, claim text, citation list, and legal status are verified against the authoritative full text and Google Patents. Descriptions of R4 and R5 are title/abstract-level only (full foreign-language text not retrieved); characterisations of R6–R10 are partly based on '155's own background section and on the cited titles, and I have not independently pulled the full specification of each 1970s-era reference. Flagging this rather than presenting them as verified full-text readings.

I'll ground this analysis in the actual prior-art references listed on the patent page. Let me pull details on the cited references.

Good grounding so far. Let me pull the remaining cited references.

Caveat on scope and sourcing

I was able to retrieve and verify full text for four of the eleven references listed in the "Citations" (prior art) section of the US5620155 page — US3758775, US3784970, US4934633, US4704610 — plus substantive disclosure detail on US4942395 and partial detail on US4704610's companion. My retrieval budget ran out before I could pull the full text of US3997868, US4775865, US4108405, JPH0260881, JPH0455163, and US5429329. Where I rely on those, I flag it explicitly and do not attribute specific disclosure to them beyond their titles and their evident field of endeavor.

Everything below is a validity-study analysis only. The patent is long dead commercially (expired for failure to pay maintenance fees effective 2005‑04‑15; anticipated expiration 2015‑03‑23), so this matters for defensive/prior-art-of-record purposes rather than litigation risk.

1. Framework

Governing law. 35 U.S.C. § 103(a) as construed in Graham v. John Deere, 383 U.S. 1 (1966), and KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007). I apply the four Graham factors: scope/content of the prior art, differences between the claims and the art, level of ordinary skill, and objective evidence of nonobviousness (there is none of record here — no secondary considerations evidence appears anywhere on the page).

Claims in issue. Independent claim 1 plus dependent claims 2–11. Claim 1 is a system claim in four means-plus-adjacency clauses:

• (a) train-borne 1st transmitter sending first electromagnetic signals sequentially to a plurality of crossing warning devices, containing (i) digitally encoded identification means specifying each crossing and (ii) digitally encoded control means;
• (b) a crossing-borne 2nd transmitter sending second signals to the train containing (i) digitally encoded crossing ID and (ii) digitally encoded operational-condition information about the warning devices;
• (c) a train-borne 1st receiver with memory to store the second signals;
• (d) a crossing-borne 2nd receiver with (i) comparison of the transmitted ID against an internally stored identity code, and (ii) control of the warning devices when matched.

Hypothetical POSITA. Bachelor's degree in electrical engineering, computer engineering, or mechanical engineering (or equivalent), plus 3–5 years' experience in railway signaling / highway-rail grade crossing warning systems and/or short-range vehicular RF data links. Such a person would know track circuits, flasher/relay and solid-state crossing controllers, RF data links with error checking, and selective/addressable (coded) activation of wayside equipment. This is a conservative, art-relevant definition; the field was mature and highly codified (AAR/AREMA standards, FRA rules) by 1995.

Analogous art. All eleven cited references are analogous: they fall in the same field of endeavor (grade-crossing protection, B61L, and highway traffic preemption) or are reasonably pertinent to the same problem (wirelessly controlling a wayside traffic/warning device from an approaching vehicle).

2. The one-sentence version

No single cited reference anticipates claim 1, but claim 1 is a predictable, KSR-style aggregation of known elements: the "wireless train↔crossing link" (US4942395; US3758775), the "digitally coded, address-compared, vehicle-initiated activation of a wayside device" (US4704610, US3784970), and "wayside self-status reporting" (JPH0455163; US4934633's warning/safe-status signaling). The genuine gaps in the cited set are the satellite positioning of claims 3–4 and 7, and the train-length turn-off computation of claims 5–6.

3. Claim 1 — element-by-element mapping

Conclusion on claim 1: every element is disclosed, but split across references. Claim 1 therefore rises or falls on motivation to combine — and the motivation here is strong and explicit (see §5).

4. Specific § 103 grounds

Ground 1 — Ferrari in view of Smith, further in view of Harmon

US4942395 → US4704610 → US4934633 (optionally with JPH0455163 for the diagnostic element).

• Ferrari supplies the bidirectional train↔crossing architecture: locomotive transceiver → crossing transceiver → coded crossing "beacon" to nearby vehicles → and a verification signal back to the locomotive operator.
• Smith supplies what Ferrari lacks: digitally coded messages, decoded and compared against a stored library at the receiver, with the comparison result pre-emptively controlling a wayside traffic-control device.
• Harmon supplies the specific wayside warning-device control implementation (alternate lamp flashing at 55 PPM, fail-safe lamp-driver logic, island-circuit presence sensing).
• JPH0455163 supplies wayside detection of an abnormal operating condition of the crossing apparatus, which is then placed in the return message to the locomotive.

Motivation: Ferrari's own stated objects include train-to-train collision proximity warning and school-bus alerting, i.e., Ferrari is expressly chasing the same "get a coded warning to the right party without a central facility" problem the '155 patent addresses. Smith is in the sub-field of addressing a coded message to a specific wayside device and acting only on a match — precisely the selective-activation problem created once Ferrari's single mobile transmitter must serve many crossings. Harmon is the art of how the crossing device is actually driven once commanded. The combination is the substitution of one known signaling path (RF command from the vehicle) for the track-circuit path into a known controller, with a predictable result.

Ground 2 — US3758775 in view of US4704610, further in view of US4942395 and JPH0455163

• US3758775 (US Department of Transportation) is the classic statement of the problem: "a major portion of signalling system costs stem from the required coupling between a warning device and a remote sensor," and the isolated track section must extend ½ mile or more. It solves it with wireless telemetry from a train-sensing location to the crossing, including "a single transmitter to protect a plurality of highway-railroad crossings," fail-safety (loss of signal → alarm), and a self-contained battery that can run 12 months unattended.
• Add Smith for digital coding and stored-code comparison.
• Add Ferrari for the crossing→train return link.
• Add JPH0455163 for the condition report.

Motivation: US3758775 states the exact problem the '155 patent attacks (cost and wiring between sensor and warning device) and the exact design constraint the '155 patent relies on (self-contained battery operation at remote crossings). It is a textbook KSR "design incentive" reference. A POSITA seeking to eliminate the ½-mile isolated track section and hard-wired coupling would be led directly to the train-borne transmitter of Ferrari/Smith.

Ground 3 — Ferrari/Smith/3758775 + US4934633 + JPH0455163/ JPH0260881 (diagnostic emphasis)

Used to knock out claim 1(b)(ii) and claim 11 specifically. The "self-diagnostic + report back" idea is not new in the field: the two Japanese references are directed to detecting abnormal conditions of the crossing apparatus itself, and US4934633 is built around a controller that internally distinguishes a "warning rate" condition from a "safe status" condition. Adding a reverse RF link (Ferrari) and a memory (routine microprocessor storage, cf. Smith's "vehicle status memory") yields claim 1(b)(ii) + claim 1(c) + claim 11.

Useful additional art outside the cited list (clearly labeled)

• US5098044 (Petit, Parker, Shahbaz; General Railway Signal Corp.; issued 1992‑03‑24; filed 1991‑07‑15) — "Highway Crossing Control System for Railroads Utilizing a Communications Link Between the Train Locomotive and the Crossing Protection Equipment." Verified full text. It discloses: a train↔crossing message interchange by radio; the crossing equipment sending a message addressed to the train; digitally coded bit fields including "crossing I.D.," approach direction, track number, and distance; a locomotive CPU with memory/database and per-trip initialization; vital (fail-safe) checks; and penalty braking if the link fails. This is materially closer to claim 1 than anything cited on the '155 page and would be the single most powerful §103 (and arguably §102) reference for the wireless-link concept. Its only real gap versus claim 1 is that crossing-ID/control information flows from a trackside beacon rather than from a stored database of crossings on the locomotive, and it emphasizes safety-state control rather than maintenance-condition reporting.
  • Source: http://patentimages.storage.googleapis.com/3d/c6/f5/fabc814aebb1a6/US5098044.pdf
• Known state of the art on solar/battery crossing power (1976 FRA/TRB literature): the FRA-funded bibliography Railroad-Highway Grade Crossings records the 1976 study "Standby Power for Railroad-Highway Grade Crossing Warning Systems," concluding that where AC primary power is very expensive, "the combination of solar cells or thermoelectric generators as the primary source, with storage batteries as standby, will be optimal." This is printed prior art squarely on claim 9.
  • Source: http://libraryarchives.metro.net/DPGTL/trb/1980-trb-bibliography-58-railroad-highway-grade-crossings-update.pdf

5. Motivation to combine — the affirmative case

Under KSR and MPEP 2143, the following show a skilled artisan would have combined these teachings:

1. Same field, same problem, same actors. Every reference addresses preventing vehicle–train collisions at grade crossings, and six of the eleven were examined/cited within B61L‑29. The Federal Railroad Administration, state DOTs, and the major suppliers (Harmon, GRS) were all actively pursuing "remove the track circuit, communicate by radio" by the early 1990s.
2. Explicit design incentive in the art. US3758775 identifies the cost of the sensor-to-warning-device coupling as "a major portion of signalling system costs" and provides a low-cost, battery-efficient wireless answer. A POSITA optimizing for remote, unpowered rural crossings would combine that goal with the coded-address techniques of US4704610.
3. Predictable result / simple substitution. Substituting an RF-coded activation signal for a track-circuit activation signal changes where the decision is made, not the physics of the crossing flasher or the legal requirement (20–30 s warning time). Predictable results = obvious (KSR).
4. Addressable coding is a known technique for a known need. Once one mobile transmitter must serve many wayside devices, collision/confusion between messages is an inevitable design problem; US4704610's stored-word comparison and US3784970's "range control" via pulse duration are the ready-made solutions. Motivating this specific improvement responds to a recognized need already identified in the art.
5. Market/competitive pressure. The 1990s migration to radio-based train control (GRS "Spacerali," ATCS) put the locomotive, not the wayside, at the center of the control architecture — the very premise of claim 1.
6. Routine automation. Claim 11 (retrieving stored messages and determining crossing identity/condition) and the memory of claim 1(c) are the automation of a known manual practice (railroad inspectors visiting crossings) using a general-purpose microprocessor memory — the classic KSR "obvious to try"/routine-implementation situation. The '155 patent's own stated benefit — letting maintenance crews skip crossings reporting all-is-well — is a business/efficiency motivation, not a technical advance.

6. Where the obviousness case is weak — honest limits

(i) Claims 3, 4, and 7 (GPS). Nothing in the eleven cited references teaches or suggests satellite positioning of a train. US3758775 uses wayside microwave telemetry; US3784970 uses RF-plus-ultrasound range gating; US4704610 uses infrared; US4942395 uses low-power shortwave proximity. On the four corners of this page's prior-art section, claims 3, 4 and 7 are not obvious over the cited art, and the examiner's allowance of the GPS-centered claims is defensible. Attacking them requires art outside the cited set (e.g., differential-GPS vehicle-location art, or the contemporaneous ITCS/PTS programs, which postdate or are simultaneous with the 1995‑03‑23 filing and would need careful date proof) or an official-notice/known-technique argument that satellite navigation receivers were commodity position sensors by early 1995. My confidence that GPS-on-a-locomotive art predating 1995‑03‑23 exists in the literature is moderate, but I could not verify a specific reference from the material available, and I will not fabricate one.

(ii) Claims 5 and 6 (train length / automatic turn-off using train-end location). The citations do not expressly teach storing train length and computing the end-of-train clearing point. Claim 6's functional result (turn warning off after the train clears) is squarely taught — US4934633's island circuit "sense[s] the presence of a stationary train at the crossing and enable[s] the same input … when a train is not present," and US3758775 relies on the absence of a train at the recorded location to restore the crossing. So claim 6 is obvious over the cited art as a result, but the specific train-length-arithmetic implementation is a gap.

(iii) The "digital" ledger. Several references are analog/pulse-coded rather than true digital packets. US4704610's 8-bit decoded word compared against a stored library is the best "digitally encoded … compared with a predetermined digital identity code stored internally" teaching in the cited set, but a patent owner can legitimately argue about the degree of digital encoding. This is a claim-construction fight (what does "digitally encoded" mean to a POSITA in 1995?), not a clean-cut mapping.

(iv) A genuine non-obviousness argument exists on fail-safety. Railroad signaling is doctrinally fail-safe: US3758775 stresses that system failure must produce a false alarm, and US4934633 is expressly built so the control circuitry "is active in creating an off condition of the warning devices." A POSITA could argue that moving crossing activation decisions onto a non-vital, single-point-of-failure locomotive radio link runs against the field's governing safety principle — i.e., a teaching away from claims 2–6. The counter is US5098044 (Petit, GRS, 1992), which had already achieved vital radio-based crossing control with integrity-checked messages and penalty braking, showing the field had overcome that concern years before the '155 filing. On balance this defeats the teaching-away argument, but it is the strongest thing the patent owner has, and it is not frivolous as to claims 4–6.

(v) Prior-art date caveat on US5429329 (Wallace). It issued 1995‑07‑04, i.e., after the '155 filing date of 1995‑03‑23. It is listed on the page as a citation, but its only possible prior-art effect is under pre-AIA § 102(e)/(a) based on its 1994‑01‑31 filing. Do not treat it as 102(b) art. It should not be relied on as the primary § 103 reference.

(vi) Confidence flags on three references. I did not retrieve full text for US3997868 (Ribnick), US4775865 (E-Lited), or US4108405 (Gibson). Based on titles and the companion US4704610 record (E-Lited is the assignee family associated with the Smith warning/traffic-control work), they appear cumulative: Ribnick and E-Lited are emergency-vehicle-warning art (vehicle transmitter → receiver alert / preemption), and Gibson is flasher-circuit art. I would not assert specific disclosures from them without pulling the documents.

7. Bottom line

Strongest invalidity theory: a three-way combination of US4942395 (Ferrari) as the base architecture, US4704610 (Smith) for the digitally coded, stored-code-compared, vehicle-initiated control of a wayside device, and US4934633 (Harmon) for the crossing warning-device controller, with JPH0455163 for wayside condition detection — with US5098044 (Petit) available as an independent, non-cited, materially closer two-way radio crossing-control reference if it can be shown to qualify as prior art (issued 1992‑03‑24, so it is unambiguously § 102(b) art against the 1995‑03‑23 filing).

Weakest link in that theory: the complete absence of any satellite-positioning teaching within the cited set, which leaves claims 3, 4, and 7 standing unless additional art is introduced.