Securus Technologies Inc v. DSI ITI LLC

1. Case Identification

• Case #: IPR2017-02203
• Patent #: 6,895,086
• Filed: September 29, 2017
• Petitioner(s): Securus Technologies, Inc.
• Patent Owner(s): DSI-ITI, LLC
• Challenged Claims: 1-20

2. Patent Overview

• Title: 3-Way Call Detection System and Method
• Brief Description: The ’086 patent relates to systems and methods for detecting unauthorized three-way telephone calls, particularly in controlled environments like correctional facilities. The technology involves filtering a telephone signal to create a narrow frequency notch, inserting a low-level white noise signal into that notch, and monitoring the amplitude of this noise signal to detect a characteristic drop that indicates a third party has been added to the call.

3. Grounds for Unpatentability

Ground 1: Claims 1-20 are obvious over Johnson in view of Rao.

• Prior Art Relied Upon: Johnson (Patent 6,141,406) and Rao (Patent 6,141,415).
• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that the combination of Johnson and Rao taught or suggested every limitation of independent claims 1 and 20, as well as all dependent claims. Johnson was asserted to teach the core inventive concept: a system for detecting unauthorized three-way calls by inserting a low-amplitude white noise signal onto a telephone line and monitoring for changes in the signal’s echo characteristics (specifically, its amplitude or power) that occur when a third party joins the call. Johnson thus disclosed the fundamental framework of measuring a baseline and detecting a shift associated with a three-way call using an injected reference signal.

    Petitioner contended that Rao, which addresses the related technical problem of double-talk detection in echo cancellation systems, supplied the specific filtering techniques that Johnson lacked. Rao taught creating a narrow frequency notch in a telephone signal using a notch filter and then using a corresponding band-pass filter to isolate and monitor the energy within that specific notched band. The combination, therefore, allegedly met all key limitations: Johnson provided the overall method for three-way call detection using white noise (meeting limitations on measuring line voltage, generating noise, determining a baseline, and monitoring for shifts), while Rao provided the specific method of using matched notch and band-pass filters for processing the signal (meeting limitations on a first filter to remove a frequency band and a second filter to pass only that band for analysis).

  • Motivation to Combine: The primary motivation asserted was to improve the performance and reduce the intrusiveness of Johnson’s system. Johnson itself acknowledged the difficulty of introducing a reference signal (like white noise) that is strong enough for reliable detection yet not a "distracting nuisance" to the parties on the call. A person of ordinary skill in the art (POSITA), seeking to solve this known problem, would have looked to analogous arts like echo cancellation, where Rao operated.

    Rao’s technique of isolating the reference signal in a narrow frequency band, outside the primary range of human speech, provided a direct and well-understood solution. A POSITA would combine Rao’s filtering approach with Johnson’s detection system to improve the signal-to-noise ratio of the detection measurement, reduce interference with the voice call, and make the reference signal less perceptible to users. The petition argued this combination represented a predictable application of known techniques to achieve a more reliable and stealthy detection system.

  • Expectation of Success: Petitioner asserted a POSITA would have had a high expectation of success. The proposed combination involved integrating known, compatible signal processing techniques (filtering from Rao, detection from Johnson) that both function within standard telephone and echo cancellation frameworks. The outcome—an improved detection system with less interference—was predictable and did not require any undue experimentation.

  • Key Aspects: Petitioner highlighted that the patent examiner considered Johnson during the original prosecution but allowed the claims. However, the examiner did not have the benefit of Rao, which was issued on the same day as Johnson and was not cited. Petitioner argued that Rao provided the critical missing teachings that would have rendered the claims obvious.

4. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’086 patent as unpatentable.