VoP Gateway PSTN Backup for Emergency Calls
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Solution Overview
Problem
Voice-over-packet (VoP) technology often blocks calls to emergency services like 911, and fails to provide accurate caller location information, as the caller's number is associated with the gateway rather than a physical location.
Innovation Solution
A telephony interface system that selectively connects to either a packet-switched network or a circuit-switched network based on dialed digits, using a controller to route calls to the PSTN for emergency numbers and VoP for others, ensuring accurate caller identification and location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If VoP technology is used to reduce call costs and simplify device management, then cost and management complexity are improved, but call reliability and location accuracy deteriorate due to blocking of emergency calls and loss of location information
Solution Approach 1:
The system segments the network connection into two separate interfaces: a packet-switched network interface for cost-effective VoP calls and a circuit-switched network interface for reliable emergency calls. The controller divides call routing based on the dialed number, directing emergency numbers through the circuit-switched network while routing other numbers through the packet-switched network.
Solution Approach 2:
The telephony device is designed with multi-functionality, capable of operating on both packet-switched and circuit-switched networks. The device includes both VoP and PSTN interfaces, allowing it to function as a VoP phone for regular calls and as a traditional PSTN phone for emergency calls, combining the benefits of both network types.
2Device complexity
If VoP technology is used to associate caller numbers with gateways, then device management is simplified, but location information accuracy deteriorates because the gateway location does not reflect the caller's physical location
Solution Approach 1:
The system segments caller identification into two separate systems: VoP caller ID for regular calls and PSTN caller ID for emergency calls. The PSTN interface provides accurate location-based caller identification for emergency services, while the VoP interface handles regular calling needs.
Solution Approach 2:
The circuit-switched network interface acts as an intermediary for emergency calls, providing a reliable path that preserves accurate location information. When emergency numbers are detected, the system switches to using the circuit-switched network which maintains the relationship between caller number and physical location.
Data Source
AI summary
A telephony interface system has a controller and multiple communication interfaces to provide voice-over-packet (VoP) telephone service with PSTN telephone service as backup. The telephony interface system has a communication interface for at least one telephony device, a communication interface for the PSTN, and a communication interface for a packet-switched network. To originate a call, the telephony interface system connects the telephony device to the PSTN if the dialed digits for the call correspond to a predetermined telephone number or numbers, such as 911. Otherwise, the telephone interface system connects the telephony device to the packet-switched network.