Earin Ab v. Audio Technica US Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Earin AB (Sweden)
  • Defendant: Audio-Technica U.S., Inc. (Delaware)
  • Plaintiff’s Counsel: The Webb Law Firm; Folio Law Group PLLC
• Case Identification: 5:25-cv-01534, N.D. Ohio, 01/16/2026
• Venue Allegations: Venue is based on Defendant's residence in the Northern District of Ohio.
• Core Dispute: Plaintiff alleges that Defendant’s line of true wireless stereo (TWS) earbuds infringes a patent related to automatic power management and connection logic.
• Technical Context: The technology concerns the user experience of TWS earbuds, specifically the automated process of powering on, connecting to each other, and connecting to a host device upon removal from a charging case.
• Key Procedural History: The complaint does not reference prior litigation, licensing history, or other significant procedural events.

Case Timeline

Date	Event
2014-09-05	’120 Patent Priority Date
2016-07-26	U.S. Patent No. 9,402,120 Issued
2026-01-16	Complaint Filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 9,402,120 - *“Wireless Earbuds”*

• Patent Identification: U.S. Patent No. 9,402,120, “Wireless Earbuds,” issued July 26, 2016 (the "’120 Patent").

The Invention Explained

• Problem Addressed: The patent background section notes the growing popularity of wireless earbuds and identifies key characteristics such as physical size, convenience, user-friendliness, and operational reliability as important for market acceptance (’120 Patent, col. 1:9-23). The invention implicitly addresses the need for a seamless user experience by automating the power and connection states without manual user intervention.
• The Patented Solution: The invention describes a wireless earbud with circuitry configured for "automatic power preservation" (’120 Patent, col. 2:45-47). When an earbud is connected to a charger, it enters an "idle mode" and disconnects existing wireless links. When disconnected from the charger, it enters an "operational mode" where it automatically follows a specific logical sequence: first, it attempts to establish a "true wireless stereo" (TWS) connection with a second earbud; if successful, it operates in stereo, and if not, it falls back to a "mono wireless audio receiver" mode (’120 Patent, col. 2:54-60; Fig. 12). If operating in TWS mode, the earbud also determines its role as a "master" or "slave" device and, if master, attempts to reconnect to known host devices (’120 Patent, col. 2:61-65).
• Technical Importance: The described automated power and connection management logic aims to eliminate the need for users to manually power earbuds on or off or manage Bluetooth connections, a key feature for the user-friendliness of early TWS products.

Key Claims at a Glance

• The complaint asserts independent claim 20 (Compl. ¶19).
• Essential elements of claim 20 include:
  • A wireless earbud with an idle mode and an operational mode, comprising a housing, loudspeaker, rechargeable battery, and a main printed circuit board (PCB) with control circuitry.
  • The circuitry is configured for automatic power preservation.
  • This is achieved by detecting connection to a charger and, in response, entering the idle mode and disconnecting from a second earbud and a host device.
  • Upon detecting disconnection from the charger, the circuitry enters the operational mode by performing a sequence of steps:
    • Attempting a TWS reconnection with the second earbud.
    • If successful, operating as a TWS receiver; otherwise, operating as a mono receiver.
    • If in TWS mode, determining if it is a "master" or "slave" device relative to the second earbud.
    • If it is the master device, attempting to reconnect with a known wireless audio streaming host device.
    • If that reconnection fails, initiating a pairing procedure with the host device.

III. The Accused Instrumentality

Product Identification

• The Audio-Technica ATH-TWX9, ATH-TWX7, ATH-CKS50TW, and ATH-CKS30TW+ Wireless Earbuds, with the ATH-TWX9 model used as a representative example (Compl. ¶¶2, 22).

Functionality and Market Context

• The complaint alleges that the Accused Products are true wireless stereo earbuds that feature automatic power management (Compl. ¶23). Specifically, they are alleged to automatically turn on (enter an operational mode) when removed from their charging case and turn off (enter an idle mode) when placed back into the case (Compl. ¶23). When removed from the case, the earbuds are alleged to automatically attempt to connect with each other to form a TWS connection for stereo audio playback (Compl. ¶33). The complaint provides a screenshot from the ATH-TWX9 user manual illustrating this automatic power on/off functionality. (Compl. p. 6). The complaint further alleges that if only one earbud is removed, it operates in a mono mode, and that establishing a TWS connection between both earbuds is required to access certain features like "L/R Balance Adjustment" in the companion mobile application (Compl. ¶¶34, 37, 39).

IV. Analysis of Infringement Allegations

’120 Patent Infringement Allegations

Claim Element (from Independent Claim 20)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
A wireless earbud having an idle mode and an operational mode, the wireless earbud comprising: an earbud housing; a loudspeaker element; a rechargeable battery; and at least one main printed circuit board having disposed thereon circuitry for wireless radio communication, audio codec and earbud operation control;	The ATH-TWX9 earbuds allegedly possess these physical components. The complaint provides visual evidence for the housing, loudspeaker, rechargeable battery, and a teardown photo showing the main PCB with its circuitry.	¶¶23-29	col. 6:36-44
wherein the circuitry is configured for automatic power preservation by: detecting connection of said battery to a charger and in response entering the idle mode, wherein existing connections to a second wireless earbud and to a wireless audio streaming host device will be disconnected;	The earbuds allegedly turn off automatically (enter idle mode) and disconnect from Bluetooth devices when placed in the charging case.	¶31	col. 9:3-9
and detecting disconnection of said battery from said charger and in response entering the operational mode by: attempting a true wireless stereo, TWS, reconnection with the second wireless earbud;	When removed from the charging case, the earbuds allegedly turn on automatically (enter operational mode) and attempt to reconnect to each other to form a TWS connection.	¶33	col. 9:15-18
if the attempt is successful, operating the wireless earbud as a TWS audio receiver and otherwise operating the wireless earbud as a mono wireless audio receiver;	If both earbuds are removed, they allegedly operate as a TWS receiver. If only one is removed, the TWS connection attempt fails, and the single earbud allegedly operates as a mono receiver. The complaint includes screenshots from a companion app showing battery levels for both earbuds (TWS) or one (mono). (Compl. p. 11).	¶34	col. 9:19-23
if operated as a TWS audio receiver, determining whether the wireless earbud is a master device or a slave device with respect to the second wireless earbud;	The complaint alleges that, consistent with the Bluetooth Core Specification, one earbud in a TWS pair necessarily assumes the role of a "master" and the other a "slave," and that the Accused Products perform this determination.	¶40	col. 9:24-29
if the wireless earbud is determined to be a master device, attempting to reconnect with the wireless audio streaming host device and other known wireless audio streaming host devices if applicable;	After being removed from the case, the earbuds allegedly attempt to automatically reconnect with previously paired host devices ("Device 1" and "Device 2"). The complaint provides packet logger screenshots showing a "Connection Request" from the earbuds to the known hosts. (Compl. p. 19).	¶¶42-43, 47	col. 9:30-34
and if reconnection with the wireless audio streaming host device fails, initiate a pairing procedure with the wireless audio streaming host device and other known wireless audio streaming host devices if applicable.	The complaint alleges that if the earbuds are removed from the host devices' list of known devices, the automatic reconnection fails. Instead of a "Connection Request," the earbuds are alleged to initiate a new pairing procedure by sending an "Inquiry Result – EIR" event to advertise their availability. This is supported by packet logger screenshots showing this different behavior under failed reconnection conditions. (Compl. p. 22).	¶¶48, 50	col. 10:45-50

Identified Points of Contention

• Scope Questions: The analysis may focus on whether the standard operational logic of Bluetooth TWS systems, which the Accused Products appear to follow, inherently meets the specific sequence of limitations in claim 20. A question for the court could be whether merely operating according to the Bluetooth standard is sufficient to prove infringement of the patent's specific method steps, such as the explicit "determining" of a master/slave role.
• Technical Questions: A factual question may arise regarding the final step: "initiate a pairing procedure." The complaint provides packet logger evidence showing the earbuds send an "Inquiry Result – EIR" when reconnection to a known device fails (Compl. ¶50). The dispute may turn on whether this "Inquiry Result" process constitutes "initiat[ing] a pairing procedure" as that phrase is understood in the context of the ’120 Patent, or if the patent requires a different or more specific set of actions.

V. Key Claim Terms for Construction

• The Term: "determining whether the wireless earbud is a master device or a slave device"

• Context and Importance: This step is a critical part of the claimed operational logic. The infringement allegation relies on the assertion that this determination is a necessary function of TWS operation under the Bluetooth standard (Compl. ¶¶40-41). The construction of "determining" will be central to whether the accused device's inherent operation satisfies this active limitation.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specification discusses the master/slave concept in the context of standard Bluetooth-based streaming and a power preservation scheme, stating that "one of the earbuds will have a role as master device with respect to the other... which will correspondingly be a slave device" ('120 Patent, col. 10:50-55). This may support an interpretation where any process that results in the establishment of a master/slave relationship constitutes "determining."
  • Evidence for a Narrower Interpretation: The claim language requires an affirmative step of "determining." The flowchart in Figure 12 shows this step (146, 148) as a distinct decision point in the logic after a TWS connection is established (140) but before reconnection to a mobile device is attempted (150, 154) ('120 Patent, Fig. 12). This could support a narrower reading that requires proof of a specific, discrete logical operation beyond the mere result of one earbud becoming the master.

• The Term: "initiate a pairing procedure"

• Context and Importance: This is the final claimed step, triggered only by a failure to reconnect to a known host. The complaint's evidence hinges on equating a Bluetooth "Inquiry Result" event with this claimed step (Compl. ¶50). The viability of the infringement allegation for this element depends on this equivalence.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specification states that if reconnection fails, a "more time and power consuming pairing procedure... will be initiated" ('120 Patent, col. 10:45-50). This language could be read broadly to encompass any action that begins the process of establishing a new connection with a host, such as advertising availability via an inquiry result.
  • Evidence for a Narrower Interpretation: The flowchart in Figure 12 depicts this step as "Go into mobile paring [sic] mode" (160) ('120 Patent, Fig. 12). This phrasing might be argued to imply a more specific state or sequence of events than simply sending an inquiry result, potentially requiring a mode where the earbud is actively waiting for a user to select it from a list on the host device.

VI. Other Allegations

The complaint does not provide sufficient detail for analysis of indirect or willful infringement.

VII. Analyst’s Conclusion: Key Questions for the Case

• A core issue will be one of functional mapping: Does the operational logic of the Accused Products, which appears to follow standard Bluetooth TWS protocols, perform the exact sequence of discrete steps recited in claim 20? Specifically, does the evidence show an explicit "determining" of the master/slave role, or is this role simply an inherent outcome of the TWS connection process?
• A key question of definitional scope will be whether the accused earbuds' act of broadcasting an "Inquiry Result" after a reconnection failure constitutes "initiat[ing] a pairing procedure" as required by the final limitation of claim 20, or if the patent's language requires a more specific set of actions.
• An evidentiary question will be the sufficiency of the technical proof. The complaint relies heavily on packet logger data to demonstrate the claimed logical flow. The case may turn on whether this data, as interpreted by experts, provides unambiguous proof that the accused software executes each claimed step, as opposed to merely producing outcomes that are consistent with those steps.