Dial Tone Detection Using Duty Cycle Verification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for detecting dial tones across multiple countries are prone to misdetection due to expanded upper and lower limit values for ON-time and OFF-time, leading to erroneous fax transmissions when sounds with similar frequencies are misinterpreted as dial tones.
Innovation Solution
An image processing apparatus that determines whether a received signal is a tone signal, measures its length, checks for specific patterns, and verifies the duty cycle within given ranges using a reduced number of cadence patterns, thereby reducing misdetections by employing additional check conditions and duty cycle verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the upper limit and lower limit values of ON-time and OFF-time are expanded to cover dial tone standards of multiple countries, then the adaptability to different countries is improved, but the measurement precision of dial tone detection deteriorates
Solution Approach 1:
The patent divides the detection process into multiple stages: first detecting the presence of a tone signal, then measuring its length, checking for specific patterns, and finally verifying the duty cycle. This segmentation allows the system to use a single pattern table while maintaining both multi-country adaptability and detection precision through progressive filtering.
Solution Approach 2:
The patent introduces dynamic duty cycle verification that adapts to the detected tone signal characteristics. The duty cycle check dynamically adjusts the detection criteria based on the measured tone signal properties, allowing the system to maintain high precision across different country standards without requiring multiple static pattern tables.
2Adaptability or versatility
If the upper limit and lower limit values of ON-time and OFF-time are expanded, then the adaptability to different countries is improved, but the reliability of detection deteriorates due to increased misdetection
Solution Approach 1:
The patent performs preliminary detection steps before final confirmation: first checking if a tone signal is present, then measuring its length, and verifying its pattern. These preliminary actions filter out false positives early in the process, ensuring that only signals meeting all criteria are confirmed as dial tones, thus maintaining high reliability across multiple countries.
Solution Approach 2:
The patent implements a feedback mechanism where the duty cycle determination is based on previously measured tone signal characteristics. The system uses the measured length and pattern information to inform the duty cycle check, creating a feedback loop that continuously refines the detection accuracy and reduces misdetection rates.
3Device complexity
If a single pattern table with expanded values is used, then the device complexity is reduced, but the measurement precision of dial tone detection deteriorates
Solution Approach 1:
The patent changes the detection parameters progressively through multiple stages: first detecting tone presence, then measuring duration, checking patterns, and finally verifying duty cycle. This parameter-based approach allows a single pattern table to effectively cover multiple country standards while maintaining precision through staged parameter verification.
Data Source
AI summary
An image processing apparatus that covers standards of a dial tone for a plurality of countries with a relatively small number of pattern tables and reduces the number of times that a sound is misdetected as a dial tone, a method for controlling the same and a program are provided. To accomplish this, the image processing apparatus measures a length of a tone signal received from outside; determines whether an intermittent dial tone including the measured tone signal and a previously received tone signal has a specific pattern or not; and determines whether a duty cycle of the intermittent dial tone is a duty cycle within a given range or not, thereby determining whether the dial tone is valid or not.