Fax Gateway CM Tone Suppression for T.38 Protocol Fallback
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Solution Overview
Problem
Super Group 3 fax machines face connectivity issues when connected over networks using un-enhanced T.38 protocol gateways, which cannot handle V.34, 33,600 bps speed, leading to failed calls as they cannot fall back to lower speeds during handshaking over voice connections.
Innovation Solution
Suppressing the CM tone in the V.8 protocol handshaking process, allowing fax machines to fall back to Group 3 mode when the enhanced T.38 protocol is not supported, ensuring connectivity by modifying gateways to prevent CM signal transmission, enabling operation at slower speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Super Group 3 fax machines use V.34 protocol for high-speed transmission, then transmission speed is improved, but compatibility with un-enhanced T.38 protocol networks deteriorates
Solution Approach 1:
The system dynamically changes the operational parameters of the fax machine based on network capabilities. When an un-enhanced T.38 gateway is detected, the system switches from V.34 high-speed mode to Group 3 mode, adjusting the transmission speed parameter to match the network's limitations while maintaining connectivity.
Solution Approach 2:
The fax connection system implements dynamic adaptability by allowing the transmission protocol and speed to change during the connection process. The system starts with high-speed V.34 protocol but can dynamically fallback to Group 3 mode when compatibility issues are detected, making the system flexible rather than static.
2Productivity
If fax machines attempt to connect at highest speed, then transmission efficiency is improved, but connection reliability deteriorates when network cannot handle the speed
Solution Approach 1:
The system performs preliminary speed detection and capability negotiation before actual fax transmission begins. By detecting the network's T.38 gateway capabilities in advance and determining the appropriate speed mode beforehand, the system avoids connection failures and ensures reliable establishment before data transfer starts.
Solution Approach 2:
The connection process incorporates feedback mechanisms where the fax machines exchange capability information and detect network responses to determine the appropriate transmission speed. This feedback loop ensures that the selected speed is actually supported by the network, preventing connection failures.
3Speed
If T.38 gateways are upgraded to handle V.34 speed, then transmission speed capability is improved, but device complexity and cost increase
Solution Approach 1:
The T.38 gateway is designed to perform multiple functions by supporting both enhanced V.34 mode and un-enhanced Group 3 mode. This multi-functionality allows a single gateway hardware platform to handle different fax speeds and protocols, eliminating the need for separate gateways for different speed requirements and reducing overall system complexity.
Solution Approach 2:
Rather than requiring full V.34 capability in all gateways, the system allows partial support where gateways can operate in un-enhanced mode for compatibility purposes. This partial action approach enables basic fax functionality across older, simpler gateways while reserving enhanced capabilities for when needed, reducing the complexity burden on all gateway devices.
Data Source
AI summary
An improved method and system for connecting Super Group 3 fax machines over network gateways that operate using the un-enhanced T.38 protocol. With the present invention, the CM tone is suppressed. Thus a gateway that generates an AnsAm tone, will not receive a CM tone in response. The T.38 protocol does not specify what occurs if a CM tone is not received; however, it has been found that, in practice, existing fax machines fall back to V.21 mode if a CM tone is not received.