VoIP Security Communicator
Custom-designed VoIP digital communicator with modular PCB architecture, SIP/VoIP stack, and multi-protocol support for real-time security alerts.
The Challenge
A UK-based security systems company needed a custom VoIP digital communicator — a device that transmits security alerts in real-time when alarms trigger. The system required custom hardware design from PCB level, supporting multiple sensor inputs, high-fidelity audio, and flexible communication via LTE, WiFi, BLE, and Ethernet.
Our Approach
We designed and delivered a complete hardware-software stack, from schematic capture and PCB layout through firmware development and protocol integration.
Modular Hardware Architecture
A three-board modular design supports two variants: a Raspberry Pi CM4-based Linux board for full-featured deployments, and an ESP32-based MCU board for cost-sensitive installations. Both share a common audio and I/O board.
Audio & Communication
A dedicated audio codec with hardware-level echo cancellation ensures high-fidelity voice over SIP. The SIM7600 LTE module provides cellular connectivity with WiFi, BLE, and Ethernet as fallback options.
Protocol Stack
The firmware implements the SIP/VoIP stack for voice communication and SIA DC09 messaging protocol for alarm signaling over TCP/IP. Auto-failover between communication channels ensures alerts always get through.
Technical Stack
- Hardware: RPi CM4, ESP32, SIM7600, dedicated audio codec
- Protocols: SIP/VoIP, SIA DC09, TCP/IP, UART
- Firmware: Embedded Linux, FreeRTOS
- Languages: C/C++, Python (Flask for configuration)
- PCB: Custom 3-board modular design
Results
- Robust end-to-end security communication stack
- High-fidelity audio over SIP with echo cancellation
- Configurable digital/analog I/O with isolated protection
- Real-time alerts with automatic channel failover
- Plug-and-play board extensibility for future sensors