Invalidity dossier
US 3660675
Transmission line series termination network for interconnecting high speed logic circuits
Current assignee: Honeywell Inc
Added 9/21/2026, 10:31:07 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 3,660,675
Title: "Transmission line series termination network for interconnecting high speed logic circuits"
Assignee: Honeywell Inc. (original assignee). Inventor: John R. Andrews Jr.
Dates: Priority/filing date 1970-05-05; granted and published 1972-05-02; anticipated expiration 1989-05-02. Status: Expired – Lifetime. Classification: H03K19/017545 (interface arrangements, impedance matching circuits), among others.
Purpose: To interconnect high-speed logic circuits, especially remotely located ones, by improving noise margins and reducing reflection-caused noise on a transmission line. The excerpt notes that when a driver logic circuit drives a single-ended output line, received voltage equals driver output voltage plus induced line noise; the invention addresses this.
Plain-language scope: A logic driver (preferably TTL with a cascode/totem-pole output stage) sends a two-state signal onto a transmission line through a series termination network (50) having two elements: a non-linear impedance (52), e.g., a diode or transistor, and a linear impedance (54). When the driver drives a binary ZERO, the series impedance including the driver's output impedance equals the line's characteristic impedance, terminating the line and preventing reflections. When it switches to a binary ONE, the first (non-linear) branch, together with the output stage, applies about one-half the voltage defining a binary ONE; at the high-impedance receiver this doubles to the full ONE level, letting the receiver threshold sit midway between ONE and ZERO for a high noise margin. The network is described for driving both a nearby internal load (80) and a remote external load (60) up to 200 feet via transmission line 62.
Source: https://patents.google.com/patent/US3660675/en
What the excerpt does not establish: It is partial text and lacks claim language verbatim. It does not establish any litigation, ownership transfers, validity, or prior-art comparison, and those were not researched. Circuit details beyond the excerpt (e.g., full claim set, all embodiments, omitted figures' specifics) cannot be confirmed from the supplied text.
Generated 10/1/2026, 10:01:34 PM
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Assignment history
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Prior art
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Obviousness
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Extensions
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