US 6006148

I'll search for the specific patent number as requested, including any litigation/docket activity.

US Patent 6,006,148 — Analyst Report

Search performed

I ran two targeted searches: (1) the exact patent number plus title, and (2) 6006148 combined with "CAFC 2026 docket appeal." The first returned the authoritative patent record (Google Patents, Justia, FreePatentsOnline). The second returned no litigation, PTAB, or Federal Circuit docket activity tied to 6,006,148 — the CAFC/UPC results that came back concerned unrelated patents (e.g., Greenthread's '014, Moskowitz '913/'022, Incept). Nothing in the search results indicates any 2026 CAFC appeal involving 6,006,148, and I cannot confirm such a docket exists. The patent's own record shows it lapsed by anticipated expiration on 2017‑06‑06 ("Expired – Lifetime").

Bibliographic summary

Assignee caveat: The Google Patents "current assignee" field literally lists Symbol Technologies LLC and Bank One Corp. The chain is more nuanced: Telxon Corporation → Symbol Technologies, Inc. (assignment dated 2002‑04‑08) → Symbol Technologies, LLC (change of name, 2015‑07‑08). The "Bank One" entry traces to a 1999 security-interest reassignment (Bank One, NA), i.e., a secured lender, not an owner of record. Do not treat "Bank One Corp" as a current patent owner.

Abstract

Status information of a rented vehicle is automatically tracked during the rental period and transmitted to a selected destination computer upon driving the vehicle into a return area. Electronic vehicle monitoring circuitry is tied to existing vehicle components to track status during the rental period. The status information includes miles driven, fuel level, pickup time, drop-off time, wear and tear, etc., and is used by the destination computer to generate a bill for the rented vehicle.

Independent claims in plain language

Claim 1 — Automated vehicle return system (base station architecture).
A vehicle has monitoring circuitry that watches vehicle status parameters. A wireless transmitter on the vehicle sends that status data. At least one base station sits inside a "vehicle return zone" and receives the data when the vehicle enters the zone. Critically, the base station transmits a polling signal within the zone to trigger the vehicle monitoring circuitry to transmit its status data. The base station then forwards the received data to a host computer that processes it.

Claim 11 — Vehicle monitoring circuit (the on-board unit).
A circuit with a processor, memory, and an RF circuit (transceiver for two-way wireless communication), coupled to vehicle components. It collects vehicle data through those components and wirelessly transmits it to a destination device upon being polled by that destination device while inside a vehicle return zone.

Claim 15 — Method of returning a rented vehicle.
Steps: drive the vehicle to a predetermined location; use on-board vehicle monitoring circuitry to gather vehicle data; use a base station to poll the monitoring circuitry upon entry into a vehicle return zone; wirelessly transmit the data to the base station; forward the data to a host computer; and process it.

Claim 20 — Automated vehicle return system (host-computer-with-receiver variant).
A vehicle with an operating-parameter monitoring system and a wireless transmitter. Rather than a base station, at least one host computer sits within the vehicle return zone with its own receiver. The host computer polls the monitoring system when the vehicle enters the zone (prompting transmission of status data) and then processes the data.

Claim 30 — Automated vehicle return system (base station + separate processing device).
A vehicle with monitoring circuitry and a transmitter; at least one base station in the return zone that polls the vehicle to prompt transmission and receives the data when the vehicle is in the zone; the base station is coupled to a vehicle return processing device that processes the data. (Dependent claims 31–34 specify the processing device may be a host computer, may be in a second vehicle such as a shuttle bus, and may print a receipt.)

Claim 40 — Vehicle return system (means-plus-function).
A vehicle comprising: means for monitoring vehicle status; means for detecting entry into a vehicle return zone; means for analyzing status data; means for determining a fee to charge a user based on vehicle status; and means for printing a bill for the fee. (Dependents add means for receiving wireless communications and means for audibly communicating status information.)

Claim 43 — Automated vehicle return system (vehicle-side billing).
A vehicle with monitoring circuitry plus a base station that transmits a prompting signal within the return zone. On receiving that prompting signal, the vehicle monitoring circuit itself generates a vehicle rental charge based on vehicle status. (Dependents 44–47: circuit processes status info on the prompt; may be coupled to a printer; may charge a customer charge card; and may receive status data from an on-board computer.)

Notes and uncertainties

• Common inventive thread across independents: zone detection via a polling/prompting signal from infrastructure, vehicle-side data collection tied to existing vehicle components (fuel gauge, odometer, speedometer), and downstream charge/bill generation. Claims 43/46/47 push the billing intelligence onto the vehicle itself (autonomous-return variant).
• Prior art incorporated by reference: U.S. Pat. No. 4,504,756 ('756) (electrical speed sensor assembly / mileage sensing) and U.S. Pat. No. 4,641,523 (fuel level monitoring apparatus).
• Evidentiary limits: My bibliographic data comes from the Google Patents record and corroborating full-text mirrors (Justia, FreePatentsOnline); I did not obtain a direct USPTO PatentCenter/assignment record or a PACER/CAFC docket search in this session. If you need a definitive current ownership or litigation status, those should be verified in USPTO Assignment, PatentCenter, and PACER directly.
• No fabricated docket: I have no authoritative information of any 2026 CAFC proceeding on this patent and will not invent one. Given the patent's 2017 expiration and its 1997 priority, active 2026 appellate litigation is unlikely but not something I can rule out from the sources retrieved.

I'll run targeted litigation searches for this exact patent number.

Let me run additional targeted searches, including on the patent-holder side.

Let me search docket-aggregator sources directly and check the patent's litigation record pages.

Litigation search results — US 6,006,148

Bottom line: I found no litigation involving US 6,006,148. No district court case, ITC action, PTAB proceeding, or Federal Circuit appeal tied to this patent number appeared in any result I retrieved. I am not reporting "zero litigation" as a verified negative — I am reporting that my searches produced no case, and I cannot rule out filings that my sources do not index.

Searches run and what they returned

Case-by-case table (as requested)

I have no case to populate. I will not construct one.

Why the absence is plausible (but not proven)

• The patent's own Google Patents record shows legal status "Expired – Lifetime," anticipated expiration 2017‑06‑06, with the last recorded reassignment chain ending at Symbol Technologies, LLC (change of name, 2015‑07‑08) and a 2015 release by Morgan Stanley Senior Funding as secured party. A patent that lapsed in 2017 is an unlikely vehicle for a 2026 infringement suit.
• The "Cited By (139)" list on the patent record is downstream patent-to-patent citation activity (e.g., Micron's US 6,112,152, I.D. Systems' WO 2000/070530 A1, Caterpillar, WhereNet, Meritor, Ramseyer). Citations are not litigation and should not be read as such. If you were looking for "cases involving" this patent, the 139 forward citations are the closest thing to a footprint, and they are all prosecution, not enforcement.
• No 2026 CAFC appeal. This is consistent with the earlier report generated for this patent, which found no docket activity. I found nothing this session that changes that.

Flags and caveats

1. Date inconsistency across the two briefs. The earlier-generated section ran under a system date of 2026‑09‑22; this task brief states April 26, 2026. Neither date changes the finding, but the two sections are stamped inconsistently — worth reconciling before this goes into a file or memo.
2. Authoritative identifier discipline. All searches used the literal string 6006148 / 6,006,148. I did not search 6,006,148 variants, 6,006,048, or 6,006,184. Note one nearby number did surface independently in the results — US 6,000,608 (Alexsam v. Simon Property Group) and US 6,000,614-adjacent art is not this patent. If you want those checked, say so explicitly; I did not run them.
3. Sources not reached. I did not obtain: a Unified Patents litigation caselist page for this patent, PACER, Docket Navigator, RPX Insight, USPTO PatentCenter/Assignment, or PTAB (PTAB appears to have no proceeding; the ptacts.uspto.gov results I retrieved were for other patents). Three supplementary queries were cut off by the step limit.
4. No fabrication. There is no litigation record for US 6,006,148 in anything I retrieved, and I will not name a plaintiff or defendant for a case that does not appear in the record.

Recommended verification if you need a certified negative: pull the patent into Docket Navigator or RPX Insight by patent number, run the Unified Patents litigation caselist filtered on 6006148, and do a PACER party search on Symbol Technologies / Symbol Technologies LLC and Telxon Corporation for 1997–2017 filings. Note that the patent's own 47 claims, seven independents (1, 11, 15, 20, 30, 40, 43), would make it an expensive assertion target even during its enforceable life — a further reason an unexplained absence of litigation is not itself suspicious here.

PTAB / AIA Trial Analysis — US 6,006,148 ("Automated vehicle return system")

Note on scope: The "PTAB proceedings on file" block in this prompt is the canonical list from the USPTO Open Data Portal (ODP). Per that ingest, the ODP returns no AIA trial proceedings for US 6,006,148. I ran four supplementary web searches to look for older or unindexed proceedings (IPR/PGR/CBM combinations of the patent number and title, Unified Patents portal coverage, and "petition"/"Board" proximity searches). Nothing surfaced. Everything below reflects that empty set — I have not invented a proceeding number, a petitioner, or a panel.

Proceedings overview

Total AIA trial proceedings on US 6,006,148: 0. Breakdown: 0 active, 0 claims invalidated, 0 claims sustained, 0 settled, 0 institution denials. The defensive posture this gives a defendant is not "the patent survived two IPRs and is hardened" — it is that nobody has ever put this patent on trial at the PTAB, no claim has ever been canceled, and no petitioner is estopped, so every invalidity ground is still on the table (§ 315(e)(2) estoppel simply never attached); more importantly, the patent expired 2017-06-06, so the § 286 six-year damages lookback leaves essentially nothing recoverable.

Proceedings — none to report

Because the count is zero, there is no "{PROCEEDING_NUMBER} — {Petitioner} v. {Patent Owner}" entry to populate. Rather than pad the list, here is the audit trail and the boundary conditions.

Why zero is the expected answer here. Three structural reasons, in order of weight:

1. No assertion activity to react to. The prior section of this analysis found no litigation, no PTAB activity and no 2026 CAFC docket tied to 6,006,148. IPR filings are almost always downstream of a demand letter or complaint; with none found, a petition campaign was never triggered.
2. Terminal expiry. The record shows actual expiration 2017-06-06 ("Expired – Lifetime," anticipated expiration 2017-06-06). IPR of an expired patent is technically possible (no claim amendments are available to the patent owner), but the cost/benefit for an alleged infringer is poor because the only remaining exposure is pre-expiry damages — see the § 286 point below.
3. Filing-era economics. A CBM review under AIA § 18 was the natural vehicle for a rental-billing business method of this vintage (priority 1997-06-06, pre-AIA, G07F 17/0014 / G07B 15/00 / G07C 5/008 classifications). The CBM transitional program sunset for new petitions on 2020-09-16 (per the PTO's rule implementing Unwired Planet v. Google). By the time the patent's enforcement value was obvious in the telematics/AV era, the CBM door was shut and the patent was already expired.

Near-misses and false positives — do not confuse these with 6,006,148

My searches returned several documents containing the literal strings "'148 patent" or "6,148,258." None of them concern US 6,006,148:

• AM General LLC v. UUSI, LLC, IPR2016-01050, Patent 6,148,258 (institution decision naming APJs Kauffman, Petravick, Rice). The number is a transposition of 6,006,148, and the patent is a fuel-pump/vehicle-electronics patent in the UUSI family (U.S. 6,009,369; 5,570,666; 5,729,456). This is not 6,006,148.
• "'148 FWD" / "the '148 patent" in IPR2021-01237 and the '009-patent rehearing papers. Those refer to an unrelated parent patent in a network-security family (the Board's collateral-estoppel discussion in Trend Micro v. Cupp Computing). Not this patent.
• Unified Patents portal hit was for US 10,404,951 (vehicle event recorders), an unrelated Zebra/telematics-adjacent patent. Unified Patents appears as a petitioner in other automotive IPRs (e.g., Unified Patents, Inc. v. Carrum Technologies, IPR2019-00481, over U.S. 7,925,416) — but no Unified Patents filing against 6,006,148 was found.

Strategic summary

Claim status: all 47 claims UNTESTED at the PTAB; none canceled, none confirmed. There is no IPR certificate, no FWD, and therefore no claim-level disposition to report for independent claims 1, 11, 15, 20, 30, 40 or 43, or for dependents 2–10, 12–14, 16–19, 21–29, 31–39 and 41–47. Anyone telling you "claims 1–5 have been canceled" on this patent is wrong — that would be a fabricated disposition. The corollary is the more useful one for a defendant: the patent owner cannot point to any PTAB record of survival, and cannot claim any Article III or PTAB validation of claims 1/11/15/20/30/40/43.

Estoppel landscape: clean, in both directions. Because no IPR, PGR or CBM was ever instituted, no petitioner is subject to 35 U.S.C. § 315(e)(2) estoppel, and no patent owner has benefited from a PTAB affirmance. If you are a defendant today, there is no "reasonably could have been raised" bar, no IPR record that pins claim constructions, and no SAS-scope issue. In principle you could file an IPR on any § 102/§ 103 ground today; in practice, see the damages point below, which usually makes an IPR a waste of budget. Note also the CBM route is unavailable — the program's sunset date has passed (2020-09-16).

Pattern signals: absent. No repeat petitioner (there is no first petitioner), no serial petitioning, no PTO appeal by the patent owner, and no defensive aggregator in the chain. The only third-party attention this patent has drawn is citation traffic: the Google Patents record shows ~139 forward citations, and it was used as an "X" category reference against later applications (e.g., EP 1361703's search report cites US 6,006,148 as X against claims 1–20; EP 2482254 A3 cites it as X against claims 5–6; GB 2450014 lists it in the IDS-style reference list). The patent is more valuable as prior art than as an asserted asset. As a pure defensive matter, that means 6,006,148 itself — not any PTAB proceeding — is the thing to put in your invalidity contentions against younger rental/telematics patents.

The practical killer: expiry plus § 286. The patent expired 2017-06-06. Under 35 U.S.C. § 286, no damages are recoverable for infringement committed more than six years before the filing of the complaint. For a complaint filed on 2026-09-22 the cutoff is 2020-09-22 — and no act of infringement can post-date 2017-06-06. Every potentially infringing act therefore sits outside the statutory recovery window. That is a dispositive damages posture on its face (subject to the usual caveats about tolling/§ 282-type equitable arguments and about the exact filing date), and it is why an IPR is unlikely to be worth filing even though nothing legally bars one.

Recommended next steps

• If a demand letter cites 6,006,148 or any of its 47 claims: do not invest in an IPR. Lead with expiry (§ 286 lookback) and with the absence of any PTAB or district-court validation of claims 1, 11, 15, 20, 30, 40 or 43. There is no FWD to link to or quote for this patent — and any "Final Written Decision on 6,006,148" cited against you should be treated as fabricated or as a mis-cited sibling patent (e.g., 6,148,258; the "148" network-security family).
• Verify the ODP result yourself before relying on it. The canonical source is the PTAB E2E / ODP trial search at https://ptacts.uspto.gov/ and the decisions search at https://developer.uspto.gov/ptab-web/#/search/decisions 🔗. A zero-result query on "6006148" is the confirmation to preserve. If a proceeding is filed later, its milestones are fixed by statute: institution decision within 6 months of the petition (§ 314(b)), FWD within 12 months of institution (§ 316(a)(11)), with a possible 6-month extension for good cause.
• If you are the one with a case to make on validity (not defense): the strongest scouting leads from the record I retrieved are (i) US 6,112,152 (Micron, "RFID system in communication with vehicle on-board computer," priority 1996-12-06 — earlier than 6,006,148's 1997-06-06 filing, so a candidate § 102(e) reference), and (ii) the incorporated-by-reference hardware patents US 4,504,756 (speed sensor) and US 4,641,523 (fuel level sensor), which the specification leans on for the sensing claims 7–9, 12–14 and 23–28. I have not verified those references' operative dates or disclosures against the claims — treat them as leads to be run down, not as grounds.
• Ownership caveat carried forward: the "current assignee" field listing "Bank One Corp" traces to a 1999 security interest, not ownership; the record chain runs Telxon → Symbol Technologies, Inc. (2002-04-08) → Symbol Technologies, LLC (change of name, 2015-07-08). If you need a real-party-in-interest analysis for a hypothetical petition, confirm in USPTO Assignment and PatentCenter directly rather than from the Google Patents field.

Confidence statement: I am highly confident in the zero-proceeding result for AIA trials (ODP ingest plus four independent searches). I am not able to confirm or deny the existence of any pre-AIA reexamination with a control number I could not surface, and I have no data on litigation-driven validity challenges outside the PTAB. Absence of PTAB activity here is consistent with — and explained by — the patent's 2017 expiry; it is not evidence that the claims were validated.

I'll research the assignment chain and any litigation/NPE activity before drafting.

Assignment & Chain-of-Title Analysis — US 6,006,148

Sourcing note (read first). I worked from the Google Patents legal-events record (https://patents.google.com/patent/US6006148/en), corroborated against Justia, FreePatentsOnline/SumoBrain, and third-party corporate documents (SEC exhibit lists, press releases, Plainsite assignment reproductions). Important limitation: none of the sources I could retrieve exposed reel/frame numbers, execution dates separate from recording dates, or the "correspondent of record" field. Google Patents' legal-events module surfaces conveyance type, assignor, assignee, and a single date, but not the reel/frame or correspondent that USPTO Assignment Center shows. I will not invent reel/frame numbers or attorney names. Where the requested field is unavailable, I say so. Direct verification: https://assignmentcenter.uspto.gov/ (search "6006148") and https://patents.google.com/patent/US6006148/en#legalEvents.

Inventors

Unusual-pattern check: No evidence of inventors departing the assignee pre-filing or within 12 months of filing. Because there is only one inventor, the "all inventors left, then fire-sale" pattern cannot be tested on a per-inventor basis. I could not retrieve any departure/employment record for Strong — this is an explicit gap, not a finding.

Original assignee

Telxon Corporation (a Delaware corporation; principal place of business 3330 West Market Street, Akron, Ohio — address taken from the Telxon→Aironet assignment instrument reproduced by Law Insider).

• Line of business: portable/handheld computing terminals and wireless data networks — mobile data transaction systems, bar-code-capable handhelds, and (via its Aironet division) wireless LAN radios. Revenue ~$363M in the trailing twelve months before the Symbol deal.
• Product embodying the claims: I found no evidence that Telxon (or any successor) shipped a commercial product practicing the automated-vehicle-return claims. The disclosure reads as a systems concept (rental-lot polling of on-board monitoring circuitry with billing hand-off). Telxon's actual product line was handheld computing/wireless infrastructure. Treat "shipped a product embodying the claims" as not established.
• Current status: Acquired. Symbol Technologies launched a hostile bid in June 1998 (rejected), then completed a stock-for-stock merger in December 2000 at ~$465M equity value. Telxon's Aironet Wireless Communications division went separately to Cisco Systems (Aironet→Cisco merger paperwork executed 1999‑11‑08, recorded 2000‑05‑24, USPTO assignment reel 10859/137). Telxon as an entity ceased to exist as an independent registrant; its assets are inside what is now Symbol Technologies, LLC / Zebra Technologies. I found no Telxon Chapter 7/11 filing.

Assignment timeline

Chronological, from the Google Patents legal-events record. Reel/frame: NOT AVAILABLE from any retrieved source — do not treat these entries as verified reel/frame citations. Dates shown are as recorded in that module; for the 1997‑06‑06 entry the date is the execution/filing date, and the others read as recording dates.

1. 1997‑06‑06 (executed/recorded same date) — Reel NNNNNN/NNNN — not retrievable

   • Conveyance: Assignment of assignors' interest
   • Assignor: Strong, Jonathan D.
   • Assignee: Telxon Corporation
   • Correspondent: not retrievable
   • Context: Founder/employee invention assignment to the operating company, executed at filing.

2. 1999‑03‑30 — Reel not retrievable

   • Conveyance: Security Interest
   • Assignor: Telxon Corporation
   • Assignee: The Bank of New York (as agent)
   • Correspondent: not retrievable
   • Context: Securitization — Telxon pledging its IP as collateral during 1998–99 financial distress.

3. 1999‑04‑13 — Reel not retrievable

   • Conveyance: Assignment of assignors' interest (recorded as an "Assignment," not labeled a security interest)
   • Assignor: Telxon Corporation, a Delaware corporation
   • Assignee: Bank One, NA
   • Correspondent: not retrievable
   • Context: Lender-side interest recorded against the portfolio during the same distressed-financing window. This is the entry that produces the misleading "Bank One Corp" name in Google Patents' "current assignee" field — it is a lender interest, not an ownership transfer.

4. 1999‑09‑09 — Reel not retrievable

   • Conveyance: Release by Secured Party
   • Assignor: The Bank of New York, as agent
   • Assignee: Telxon Corporation
   • Correspondent: not retrievable
   • Context: Refinancing — prior collateral package released.

5. 1999‑09‑09 — Reel not retrievable

   • Conveyance: Security Interest
   • Assignor: Telxon Corporation
   • Assignee: Foothill Capital Corporation, as Agent
   • Correspondent: not retrievable
   • Context: Refinancing — replacement lender takes the collateral position.

6. 1999‑09‑09 — Reel not retrievable

   • Conveyance: Release of Security Interest
   • Assignor: Bank One, NA
   • Assignee: Telxon Corporation
   • Correspondent: not retrievable
   • Context: Refinancing — Bank One lien discharged in the same release package.

7. 2002‑04‑08 — Reel not retrievable

   • Conveyance: Assignment of assignors' interest
   • Assignor: Telxon Corporation
   • Assignee: Symbol Technologies, Inc.
   • Correspondent: not retrievable
   • Context: Internal/strategic merger cleanup — post-closing recordation of the Telxon→Symbol acquisition completed December 2000. This is the only true ownership transfer after the original assignment.

8. 2005‑01‑05 — Reel not retrievable

   • Conveyance: Security Interest
   • Assignor: Symbol Technologies, Inc.
   • Assignee: JPMorgan Chase Bank, N.A.
   • Correspondent: not retrievable
   • Context: Securitization — corporate credit facility collateral.

9. 2005‑10‑05 — Reel not retrievable

   • Conveyance: Release of Security Agreement
   • Assignor: Wells Fargo Foothill, Inc. (formerly Foothill Capital Corporation)
   • Assignee: Telxon Corporation
   • Correspondent: not retrievable
   • Context: Cleanup release of the 1999 Foothill collateral interest — recorded against the old Telxon name years after the merger, a common legacy-record artifact.

10. 2010‑12‑03 — Reel not retrievable

    • Conveyance: Release by Secured Party
    • Assignor: JPMorgan Chase Bank, N.A.
    • Assignee: Symbol Technologies, Inc.
    • Correspondent: not retrievable
    • Context: Securitization — 2005 collateral position released.

11. 2014‑10‑31 — Reel not retrievable

    • Conveyance: Security Agreement
    • Assignor: Laser Band, LLC; Symbol Technologies, Inc.; Zebra Enterprise Solutions Corp.; ZIH Corp.
    • Assignee: Morgan Stanley Senior Funding, Inc., as Collateral Agent
    • Correspondent: not retrievable
    • Context: Securitization — acquisition financing tied to Zebra Technologies' October 2014 purchase of Motorola Solutions' Enterprise business (which had itself acquired Symbol in 2007). Note the patent is swept into a multi-entity, cross-brand collateral package, which is how portfolios get co-pledged.

12. 2015‑07‑08 — Reel not retrievable

    • Conveyance: Change of Name
    • Assignor: Symbol Technologies, Inc.
    • Assignee: Symbol Technologies, LLC
    • Correspondent: not retrievable
    • Context: Internal reorg / change of name only — no change in beneficial ownership.

13. 2015‑08‑17 — Reel not retrievable

    • Conveyance: Release by Secured Party
    • Assignor: Morgan Stanley Senior Funding, Inc.
    • Assignee: Symbol Technologies, Inc.
    • Correspondent: not retrievable
    • Context: Securitization — 2014 collateral position released.

14. 2017‑06‑06 — Anticipated expiration; status "Expired – Lifetime."

    • Context: End of enforceable term. No further assignments recorded; no post-expiration transfers observed.

Contradiction flag vs. the previously generated section: the prior section listed the "current assignee" as Symbol Technologies LLC; Bank One Corp. The timeline above confirms that reading but sharpens it — Bank One's entry is a 1999-04-13 lender interest (item 3), not ownership. The last true ownership event is item 7 (2002, to Symbol Technologies, Inc.), and the last name change is item 12 (2015, to Symbol Technologies, LLC). Consistent with the earlier section; no conflict.

Dropped thread worth flagging: a Telxon → Aironet Wireless Communications assignment of patent applications executed 1998‑03‑30 exists and is listed as exhibit 10.8 in Telxon's SEC exhibit index (Aironet's applications 08/580,666 and 08/810,328 are the named items). US 6,006,148 is not on the Aironet→Cisco merger schedule (USPTO assignment 10859/137, executed 1999‑11‑08, recorded 2000‑05‑24; correspondent Anne VanBuskirk, Weil Gotshal & Manges LLP). Conclusion: the '148 patent was not part of the Aironet carve-out and stayed with Telxon.

Timeline diagram

timeline
    title Ownership of US 6006148
    1997 : Inventor assigns to Telxon
    1999 : Bank of New York security interest
         : Bank One security interest
         : Foothill Capital security interest
    2002 : Assigned to Symbol Technologies Inc
    2005 : JPMorgan Chase security interest
         : Foothill interest released
    2010 : JPMorgan interest released
    2014 : Morgan Stanley security agreement
    2015 : Renamed Symbol Technologies LLC
         : Morgan Stanley interest released
    2017 : Patent expires

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. The chain runs inventor → Telxon → Symbol Technologies, Inc. → Symbol Technologies, LLC. The only "IP-looking" event is item 12 (2015‑07‑08), a Change of Name from "Inc." to "LLC" — a naming conversion, not a transfer to a new vehicle. No assignee with "IP / Patents / Licensing / Holdings / Ventures" suffix appears anywhere in the record. Symbol Technologies, LLC is an operating subsidiary inside Zebra Technologies, not a single-purpose licensing LLC.

2. Known asserter in the chain — NOT PRESENT. No assignee matches any public NPE list (Acacia, Marathon, IV, Wi‑LAN, Conversant, Pendrell, Round Rock, Spangenberg entities, etc.). The nearest thing the searches surfaced was unrelated Acacia-family docket material (Monarch Networking Solutions, Starboard Value) appearing in a different patent's chain — I am expressly not importing that into this record. Independent litigation searching for US 6,006,148 returned no case naming the patent as an asserted asset.

3. Repeat correspondent across the chain — UNKNOWN / COULD NOT BE ASSESSED. This is the signal the task weights most heavily, and it is the one I cannot answer from the sources retrieved: every source exposed the legal events but none exposed the correspondent of record field. I found exactly one correspondent anywhere near this corporate family — Anne VanBuskirk, Weil Gotshal & Manges LLP — but that belongs to the Aironet→Cisco assignment (reel 10859/137), a different chain entirely, and single-appearance evidence would not satisfy the recurrence test anyway. Do not treat this item as cleared; it is an open verification gap.

4. Cascading transfers — NOT PRESENT. The transfers span 1997→2015 with no chain of LLCs. Items 4, 5, 6, 9, 10, 13 are releases of security interests, which routinely sit at the same real-property address as the lien they discharge; treating the 1999‑09‑09 triple-entry or the 2015‑08‑17 release as "cascading transfers" would be a misreading. The one genuine ownership event after 1997 is item 7 (2002).

5. Pre-litigation transfer — NOT PRESENT. No infringement suit naming this patent was identified, so there is no suit date to measure a six-month window against. The nearest ownership event (2002‑04‑08) predates any conceivable assertion by 15+ years.

6. Bankruptcy fire-sale — NOT PRESENT. Telxon's 1999 secured-lending stack (items 2, 3, 5) reflects distressed corporate financing, not a Chapter 7/11 estate sale — and the corporation was ultimately absorbed by merger, not liquidated in bankruptcy. No Kodak/Nortel-style sale of this patent was found.

7. Privateering — NOT PRESENT. No transfer from an operating company to an NPE asserting on its behalf. Symbol/Zebra retained the asset in-house through expiration.

8. Defensive aggregator — NOT PRESENT. The chain does not terminate at RPX, AST, LOT, Unified, or OIN. It terminates at an operating company (Symbol Technologies, LLC, within Zebra Technologies), and the patent simply expired on 2017‑06‑06.

Verdict

Defensive / non-asserting — with an explicit caveat on the label.

The chain of title terminates at an operating company, not at a defensive aggregator, so the category's parenthetical does not literally fit. I nonetheless select this verdict because it is the only available option consistent with the evidence: the record shows zero NPE signals (no shell entity, no known asserter, no cascading LLC transfers, no privateering, no liquidation sale), the sole ownership transfer after the original assignment is the 2002‑04‑08 Telxon→Symbol Technologies, Inc. merger cleanup, the 2015 change of name is "Inc."→"LLC" only, and the patent expired 2017‑06‑06 without any identified assertion. "Operating-company assertion" is rejected for the same reason it would be tempting — Symbol/Zebra is an operating company, but no suit asserting these claims was found. "Insufficient data" is rejected because far more than the original assignment is on record (13 further events).

Two things a reviewer must not over-read: (a) I could not retrieve reel/frame numbers or correspondents, so signal 3 is unresolved — the highest-value NPE tell remains unverified; and (b) the "Bank One Corp" name in Google Patents' current-assignee field is a 1999 lender interest and not evidence of any licensing entity ever holding title.

Verify at: https://assignmentcenter.uspto.gov/ — search patent number 6006148 to pull the reel/frame and correspondent fields I could not obtain here.

I'll search for the USPTO record and the prior-art citations for US 6,006,148.

Let me pull the actual "Patent Citations" (backward/prior-art) list for US 6,006,148 rather than the forward "Cited By" list.

Prior-Art Analysis — US 6,006,148 ("Automated vehicle return system")

Scope note up front: My search tooling reached its step limit before I could retrieve the patent face's own "References Cited" block from USPTO PatentCenter/Google Patents. Below I separate (a) what the authoritative full text you supplied lets me state with certainty, from (b) what I could not verify, and (c) a citation-direction correction that materially affects your request. I will not fabricate a citation list.

1. Citation-direction correction (important)

Your task says "look at each patent citation for 6006148." On the Google Patents record, "Cited By (139)" is the forward citation list — patents that cite 6,006,148 — not prior art against it.

That list (US 6,112,152 Micron; US 6,081,524 LG; US 6,141,610 Trimble; WO 2000/070530 A1 I.D. Systems; US 6,185,490 Ferguson; US 6,278,921 Minorplanet; US 2001/0039509 Dar; DE 10021733 Siemens; US 6,356,824 and US 6,363,304 Meritor; etc.) consists of documents that postdate the 1997-06-06 priority date. Under 35 U.S.C. § 102 (pre-AIA, applicable to this 1997 filing), a reference must predate the invention or the filing; later documents cannot anticipate claims 1, 11, 15, 20, 30, 40, or 43. So those 139 entries are legally unavailable as § 102 art against this patent, even though Google surfaces them as "citations."

The same applies to the two third-party search reports that surfaced and that cite '148:

• EP 1 361 703 A3 search report — cites US 6 006 148 A (STRONG ET AL) 21 December 1999 as an X document, alongside US 5,058,044 A (STEWART STEDMAN J, 1991-10-15) and others. Those are citations inside EP 1 361 703, not prior art in '148's own file.
• GB 2 450 014 A — lists US 6006148 A in its "Documents Cited by ISA" box. Again a forward citation.
• WO 2014/110250 A1 search report — cites US 6 006 148-family material; forward.

Only backward citations (the patent's own "References Cited" / specification incorporations) can be § 102 art. That is the correct target, and it is what I could only partially obtain.

2. Record confirmation for US 6,006,148 (USPTO data as mirrored)

I confirm this from the authoritative text and corroborating mirrors (patents.google.com/patent/US6006148A/en; Justia; FreePatentsOnline). I did not reach USPTO PatentCenter directly; treat the "current assignee" display (Symbol Technologies LLC; Bank One Corp) with the same caveat flagged in the earlier section — the Bank One entry is a 1999 security interest, not ownership.

3. Backward citations (prior art) — what the authoritative text establishes

The supplied full text of US 6,006,148 contains no "References Cited" section (the Google Patents web rendering omitted it). The only prior-art references it explicitly identifies and incorporates by reference are two US patents:

Reference A — US 4,504,756 ("'756")

Reference B — US 4,641,523

These are the only two prior-art references I can state with certainty were cited in US 6,006,148.

4. § 102 anticipation analysis

Bottom line: neither confirmed reference anticipates any claim of US 6,006,148.

Both JP-priority, 1980s-era sensor patents predate the 1997-06-06 filing by more than a decade, so both qualify as prior art under pre-AIA § 102(b). But § 102 anticipation requires a single reference disclosing every limitation of the claim. Each of the seven independent claims requires a combination of elements — vehicle monitoring circuitry, a wireless transmitter/receiver, a vehicle return zone, and (in most independents) a polling/prompting signal from infrastructure, plus host-computer processing and/or charge generation. Neither '756 nor '523 discloses wireless communication, a return zone, polling, or billing. They are component-level art, not system-level art.

Per-claim mapping (best-case relevance, all § 103 obviousness at most, not § 102):

So the correct characterization is: '756 and '523 are the most relevant confirmed prior art for the sensor sub-elements of '148, and are § 103 combination material; they do not singly anticipate any of claims 1–47.

5. What I could not obtain (explicit gaps)

I could not retrieve the examiner-cited "References Cited" block for US 6,006,148, so I cannot rule out that the patent face lists additional U.S. patent references (e.g., a US 5,058,044-style automated-vehicle-monitoring patent, or other fleet/rental/telemetry art). Specifically:

• No direct USPTO PatentCenter "References Cited" or file-wrapper retrieval completed.
• No confirmation of the total count of backward citations (the "Patent Citations (82)" figure that appeared in my results belongs to the page for US 6,112,152 (Micron), not to '148 — do not transfer that number).
• I did not verify titles or citation status for candidate art such as US 5,058,044 A (Stewart Stedman J., 1991-10-15), which surfaced only as an X reference within EP 1 361 703's search report, not within '148's file. I have not confirmed its title, and it must not be attributed to '148's citation list without verification.
• Tool step limit cut off follow-up queries (US 5,058,044 detail; direct Google Patents "Patent Citations" block for US6006148A).

6. Flags

1. Identifier discipline observed. All queries used the literal strings 6006148 / 6,006,148 / US6006148A. No nearby numbers were substituted. Adjacent numbers surfaced incidentally and are flagged as not this patent: US 6,000,608, US 6,112,152, US 6,081,524, US 6,141,610.
2. Date inconsistency (carried forward). The earlier sections were stamped 2026-09-22 (system date) while this task brief states April 26, 2026. Neither date changes the analysis, but reconcile the stamps before filing.
3. No fabrication. I am reporting two confirmed incorporated-by-reference prior-art patents; I am not inventing a citation list, a title, or an anticipation conclusion I cannot support.

7. Recommended verification (to close the gaps)

1. Open USPTO PatentCenter → Application 08/871,878 → "References Cited" / "Patent Citations" and export the examiner-cited U.S. patent list; this is the definitive § 102/§ 103 art set.
2. Cross-check the same list on Google Patents → US6006148A → "Patent Citations" (backward block only; ignore "Cited By").
3. Pull the file wrapper (Image File Wrapper) for 08/871,878 to see any examiner § 102/§ 103 rejections and the art actually relied upon during prosecution — that is the strongest signal of the art the examiner considered most relevant.
4. If you want me to analyze specific references once retrieved, supply the citation list and I will map each reference to claims 1, 11, 15, 20, 30, 40, 43 element-by-element under pre-AIA § 102(a)/(b)/(e).

I'll ground this obviousness analysis in the actual prior-art record. Let me pull the references cited on the face of 6,006,148, the two references incorporated by reference, and the pre-1997 candidates from the forward-citation list.

The forward-citation list on Micron's US 6,112,152 just exposed a set of pre-1997 references that map onto this patent's claims. Let me pull those operative references.

I hit the tool-call limit mid-search, but I retrieved enough of the operative record to build the analysis. Below is the § 103 opinion, grounded in the references I actually pulled.

Obviousness Analysis — US 6,006,148 under 35 U.S.C. § 103

Bottom line up front

The claims of US 6,006,148 are, in my assessment, more likely than not invalid as obvious over a small, well-documented set of pre-1997 references — with two important qualifications:

1. The strongest ground does not require the patentee's own incorporated references at all; it runs on US 5,289,369 (Hirshberg, "Car rent system") in view of US 5,995,898 / US 6,112,152 (Tuttle, Micron, "RFID system in communication with vehicle on-board computer") — the latter being § 102(e) art with a 1996‑12‑06 filing date, six months before the 6,006,148 filing date of 1997‑06‑06.
2. The remaining kernel — automatically finalizing a rental transaction because the vehicle drove into a defined return zone — is the only limitation not squarely and expressly met by a single reference. That is a KSR "obvious to try / finite number of identified solutions" gap, not a missing element, and I think it closes. But it is the honest weak point, and I flag it below.

Note: this analysis is untested in any forum. Per the earlier sections of this report, there is no IPR/PGR/CBM, no litigation, and no FWD (Federal Circuit or otherwise) on this patent. Everything here is a prospective defense-side opinion. Also carried forward: the expiry on 2017‑06‑06 and the § 286 six-year lookback mean no live damages either way — this analysis matters for (a) rebutting a demand letter, and (b) using 6,006,148 as your prior art against younger rental/telematics patents. The date inconsistency flagged earlier (task date April 26, 2026 vs. the system stamp 2026‑09‑22) does not change any conclusion.

1. Governing law and framework

Because US 6,006,148 was filed 1997‑06‑06, pre-AIA § 103 governs (AIA §§ 3(n)(1) applies only to applications filed on or after 2013‑03‑16). The analysis is therefore Graham v. John Deere Co., 383 U.S. 1 (1966) — scope/content of the prior art, differences, PHOSITA level, secondary considerations — as glossed by KSR Int'l Co. v. Teleflex Inc., 550 U.S. 398 (2007): the TSM test is not the sole test; a combination of familiar elements according to known methods is obvious when it does no more than yield predictable results (KSR at 416); where a design need presents "a finite number of identified, predictable solutions," that is a § 103 ground (id. at 421). MPEP § 2143 (rationales), § 2144.03 (common knowledge), § 2145 (design variations) supply the operational checklist.

Level of ordinary skill (proposed): a bachelor's degree in electrical engineering or computer science, or equivalent, plus 2–3 years of experience with RF data-collection (bar-code/RFID), vehicle sensor/computer interfaces, and transaction-processing software; or a master's degree with less experience. Critically, by June 1997 the RF-interrogator arts and the vehicle-on-board-computer arts were each mature, crowded, and cross-citing.

Claim construction points that matter:

• "Vehicle return zone" (claims 1, 11, 15, 20, 30, 39, 43) is a functional/geographic limitation; the specification itself defines it capaciously — "any region in which the vehicle can wirelessly transmit information to a device which receives the information for purposes of completing… a transaction related to returning the vehicle." That breadth helps the obviousness case: it reads on any fixed-location RF reader/interrogator deployed at a rental lot.
• Claim 40 is means-plus-function; under pre-AIA § 112 ¶ 6 the corresponding structures are processor 260, memory 264, RF section 270 (antenna 280 / receiver 282 / transmitter 284), A/D 300, magnetic sensor 340, fuel-level apparatus 410/330, and printer 600 (FIG. 12). Obviousness of a 112 ¶ 6 claim is assessed on the underlying function and the corresponding prior-art structure.
• The "polling signal / prompting signal" element (claims 1, 11, 15, 20, 30, 39, 43) is the single most important disputed term, because it is the supposed point of novelty over the manual-status-report prior art.

2. The prior art I verified (with dates and status)

Two structural facts about this record are themselves evidence:

• The patentee's own admissions. The 6,006,148 Background concedes that rental agencies already used employees with "a wireless portable computer" to check mileage and fuel at drop-off and send the data "instantaneously… to the computer of the attendant inside the rental establishment." That is an admitted prior-art system practicing the entire commercial purpose, minus automation of the sensing and the trigger. The specification also states that "several brands of vehicles include on-board computers which collect data such as fuel level, speed, mileage," and calls voice-synthesizer chips "readily available from several manufacturers." Admissions in the specification are usable as prior art without further corroboration.
• Cross-citation / crowded art. US 6,112,152's own front page lists US 6,006,148 among its cited references, and 6,006,148's forward-citation list carries 6,112,152 — the two are mutually cited, same-field art. The Tuttle reference in turn cites a dense web of interrogate/respond and vehicle-monitoring art (e.g., US 4,075,632 Baldwin, "Interrogation and detection system," 1978; US 5,621,412 Sharpe, "Multi-stage transponder wake-up"; US 5,686,920 Hurta, "Transponder maintenance mode method"; US 5,649,296 MacLellan, "Full duplex modulated backscatter system"). That is textbook § 103 "crowded art" / common-knowledge support.

3. Claim-element mapping and the grounds

Ground 1 (primary): Hirshberg '369 + Tuttle '898/'152

The sole meaningful difference from claim 1 as a whole is the automatic zone-entry trigger. Motivation to combine (MPEP § 2143, rationales (A), (B), (C), (F), (G)):

• Same field, same problem, same disclosed purpose. Both references address automating fleet/rental vehicle transactions via wireless vehicle data; KSR holds that a combination of elements from the same field to address the same need is obvious.
• Simple substitution of a known element for a known element. Hirshberg's renter must "actuate certain indication means" to terminate the hire so central control can "bill him." Tuttle replaces a manual initiation step with an interrogation event. Substituting an automatic RF interrogation trigger for a manual actuation, to achieve the same result (initiate settlement of the transaction), is the paradigm "substitution of one known element for another" (KSR at 416; MPEP § 2143).
• Express teach/cite. Tuttle expressly contemplates its interrogator at a "service center… dealership… parking lot" — i.e., fixed sites where vehicle-transaction data is collected. That is an express lead toward a rental-lot reader.
• The patent's own admission of the wireless-portable-computer drop-off practice shows the industry was already combining wireless vehicle-status capture with host-side billing — so the only remaining design question was "how to trigger the upload," and polling was the best-known answer in the RFID art.

Under KSR, this ground renders claims 1, 5, 6, 7, 10, 11, 15, 16, 17, 18, 19, 20, 25, 26, 27, 29, 30, 31, 35, 37, 38, 39, 43 and 44 obvious.

Ground 2: Ground 1 + US 4,504,756 + US 4,641,523 (the patentee's own incorporations)

The '148 specification expressly incorporates '756 (transmission-shaft magnetic speed sensor) and '523 (float/resistance-rod fuel gauge) to supply the sensing hardware. A patentee cannot rely on those references being non-analogous or incompatible with its own claims when its own specification builds the claimed sensing elements on them (and, in any event, both are § 102(b) art). This ground squarely closes the sensing sub-claims: 8, 9, 12, 13, 14, 23, 24, 28, 36, 37.

Ground 3: Ground 1 + conventional POS/portable-printer art (bill-printing and remote-terminal claims)

Claims 32, 33, 34, 40, 42, 45 require a processing device in a second vehicle (a shuttle bus) and a printed bill/receipt. The specification itself concedes the shuttle-bus computer "could be coupled to a printer (not shown) which could print out a final bill." Motivation: putting the receipt-generation terminal where the departing customer physically is (the shuttle) is a known technique applied to a known device, ready for improvement (MPEP § 2143 rationale (D)); portable/handheld terminal-with-printer art of the mid-1990s (including the assignee Telxon's own field) supplies the structure. This is my weakest ground because I did not verify a specific printer reference this session — see § 6.

Ground 4: Ground 1 + Tuttle's card circuitry, for the charge-card and autonomous-return claims

Claims 40, 41, 43, 44, 45, 46, 47. Tuttle '152 expressly discloses credit-card circuitry 62 that stores a credit card number in vehicle memory and transmits it to a transponder to make a payment, plus debit-card circuitry 60. Hirshberg discloses card-based customer authorization and central-control billing. The combined teachings therefore disclose "charges based on fuel level… mileage… time returned" (Hirshberg's monitored parameters) applied to a stored account number (Tuttle) — i.e., claims 43 and 46. Claim 47 (status info from an on-board computer) is expressly Tuttle's on-board computer 12 and expressly admitted in the '148 specification. Claim 45 (vehicle-coupled printer) is the printer art of Ground 3.

Motivation for the vehicle-side-computation variant (claims 43–47) specifically: this is the cleanest "obvious to try" posture in the patent. Once the data and the customer's account are on board, there are exactly three identified, predictable places to compute the charge — host, base station, or vehicle. Choosing the vehicle is a finite, predictable design option, and distributive processing onto embedded controllers was a recognized design trend. KSR at 421. Nothing in the claims produces a new physical result beyond the expected sum of the parts.

4. The patentee's best counterarguments, and why I think they fail

(a) "Hirshberg teaches away — return is to any random parking place, not a fixed zone." Partially fair. But: (i) Hirshberg's system still has fixed authorized parking places and a central-control station; (ii) Tuttle, Benson, and the AVI art already deploy readers at fixed geographic sites; (iii) 6,006,148's own definition of "vehicle return zone" is so broad that it reaches any such site; and (iv) the problem the patent addresses — reducing labor at an agency drop-off — inherently presupposes a rental agency lot. A teaching-away argument requires the reference to criticize, discredit, or otherwise discourage the claimed solution; Hirshberg's flexible-location model does none of those things with respect to how the termination is signaled.

(b) "Polling is the point of novelty; the art triggers by manual actuation." The claim language itself treats the polling signal as a mere trigger ("to trigger the vehicle monitoring circuitry to transmit"). Interrogator-triggered response is the defining, ubiquitous primitive of RFID/AVI — as the dozens of wake-up/backscatter/interrogation references on the face of Tuttle demonstrate. Automating a trigger is a predictable variation, not an inventive leap.

(c) "The specific agency-return workflow was never combined." This is the "combination must be taught" argument KSR rejected. Where the references are in the same field and address the same need, a motivation from the problem itself suffices (see also In re Icon Health & Fitness).

5. Secondary considerations

I see no objective evidence of non-obviousness in the record I retrieved:

• No nexus: the commercial success (if any) of rental-drop-off automation is attributable to business-method practices and then-prevailing market forces (the '148 Background itself cites airline ticketless-travel pressures), not to any claimed technical advance.
• No unexpected results: every claimed function (sense mileage/fuel, transmit wirelessly, poll, forward to host, compute charge, print) performs exactly as the prior art predicts.
• No copying, no licensing program, no industry praise, no long-felt-but-unsolved need surfaced in any source I retrieved. Given the patent's 2017 expiry and the absence of any litigation or PTAB record (per the earlier sections of this report), there is no evidentiary record in which such factors were ever developed.

6. Evidentiary limits — read this before relying on any of the above

I want to be explicit about what I did not verify, because a § 103 opinion is only as good as the references behind it:

1. I did not retrieve the front page "References Cited" list of US 6,006,148 itself. The examiner's own cited art is the single best starting set for an obviousness position, and I could not pull it this session (three supplementary queries — on Widl '678, Benson, and Hirshberg follow-ups — were cut off by the tool step limit). This is the largest gap. Before filing anything, pull the full document from https://patents.google.com/patent/US6006148/en and read the "References Cited" block.
2. US 5,721,678 (Widl, "Arrangement for a use billing system", 1998‑02‑24) and US 5,729,740 (Tsumura, "Information service billing system using radio communications", 1998‑03‑17) both issued after the 1997‑06‑06 filing. They are only usable as § 102(e) art if their US filing dates predate 1997‑06‑06 — I did not verify their filing dates.
3. US 5,635,693 (Benson) — I have the title, the 1997‑06‑03 issue date and the EP 0 725 377 A companion (1996‑08‑07) from the face of US 6,112,152; I did not read the specification, and the US number should be confirmed against the source.
4. WO 93/04353 and WO 94/07206 — title, date, and citation on the Micron face only; contents unread.
5. No voice-annunciation reference (claims 2, 21, 42) and no vehicle/printer POS reference (claims 34, 40, 45) was verified. The specification's own statements that voice chips are "readily available" and that a bus computer could drive a printer support these as admissions/design-choice grounds, but I have no specific anticipating/obviousness reference in hand.
6. Actual invention date unknown. If 6,006,148's inventors can swear behind 1996‑12‑06 (pre-AIA Rule 131, or an earlier conception/reduction to practice), Tuttle '898/'152 loses its § 102(e) status. That would weaken, but not eliminate, Ground 1 (Hirshberg '369 alone remains § 102(b) and covers most of the platform; the polling element would then need to come from the older RFID art such as Baldwin '632, Sharpe '412, Hurta '920, or WO 93/04353).
7. No prosecution history / file wrapper was obtained, so I cannot say whether the examiner already considered and distinguished Hirshberg or Tuttle.

7. Recommended next steps

1. Retrieve the '148 front-page references and file wrapper (Google Patents / USPTO PatentCenter). If Hirshberg '369 or Tuttle appears there, an obviousness challenge is materially stronger than if it does not.
2. Verify the four § 102(e) dates in item 2–4 above via PatentCenter's continuity data.
3. Draft the primary ground as: Hirshberg US 5,289,369 in view of Tuttle US 5,995,898 (or US 6,112,152), and further in view of US 4,504,756 and US 4,641,523, and optionally a POS-printer reference. Map every limitation of each challenged claim with a pinpoint cite; do not rely on a conclusion of "the references are analogous."
4. Preserve the defense-side use case: regardless of validity, 6,006,148 is a strong prior-art weapon against younger rental/telematics patents — its 1997‑06‑06 priority and 139 forward citations make it a natural primary reference. That is where this patent has residual value.
5. If a demand letter arrives: lead with the 2017‑06‑06 expiry and § 286 lookback (as developed in the earlier sections), and hold this obviousness analysis in reserve. Given the expired status, no IPR is worth funding — but this analysis is exactly what you would use in an invalidity contention or a covenant-not-to-sue posture.