I Built a Circuit Breaker for Phone Lines So Customers Never Hear Dead Air

Description and use

A telecom-native circuit breaker automatically fails over voice calls to a backup carrier during outages, preserving customer experience and trust.

Problem

Phone lines fail, causing customers to hear dead air and lose calls, especially critical for banks, hospitals, and emergency services.

Outcome

The circuit breaker ensures continuous voice service during carrier outages, maintaining customer trust with a brief outage announcement and preventing call loss.

Workflow

• 1. Detect suspicious transaction and initiate fraud alert call via primary carrier.
• 2. Monitor carrier webhooks for call outcomes (busy, no-answer, timeout).
• 3. Increment failure counter on each failure webhook.
• 4. Trip circuit breaker after threshold (default 3) and route new calls through backup carrier.
• 5. After cooldown, enter half-open state and probe primary carrier with a live call.
• 6. If probe succeeds, close breaker and route future calls to primary; otherwise keep open and continue using backup.

Evidence

The system has two independent Telnyx Call Control connections. A router sits in front and watches for failure signals.

Source

When failures accumulate — busy, no-answer, timeout — the breaker trips at a threshold and all new calls route through the backup connection.

Source

The backup announcement doesn't hide the outage — it says "we're running on our backup systems right now."

Source