Telephony Engineer - FreeSWITCH/VoIP

About the Role :

Looking for someone who can take a FreeSWITCH deployment from zero to production and keep it running smoothly at scale. You'll be the go-to person for everything voice - from call routing logic to WebRTC integrations to keeping calls crystal clear under load.

The Work :

FreeSWITCH Platform :

- Stand up FreeSWITCH environments from scratch and keep them running in production.

- Full ownership of call flows, dialplans, IVR design, conferencing, and routing logic.

- Set up SIP profiles (internal and external), gateways, trunks, and extensions.

- Architect for multi-tenancy and high availability.

Voice Protocols & Networking :

- Deep familiarity with SIP signaling, RTP media streams, and SDP negotiation.

- Fix audio issues - one-way audio, dead air, dropped calls, failed registrations.

- Handle NAT traversal, firewall setup, and RTP port configuration.

- Read SIP traces using tools like siptrace, sngrep, and tcpdump.

Scripting & Call Logic :

- Write dialplans across XML, Lua, JavaScript, or Python.

- Build call queue logic (inbound and outbound), time-based routing, skill-based routing, and failover paths.

Systems Integration :

- Connect FreeSWITCH with CRM/ERP tools, billing systems, voice bots (ASR/TTS), and external APIs over WebSocket or REST.

- Leverage ESL - both inbound and outbound - for live call control and monitoring.

Browser Calling & WebRTC :

- Configure WebRTC (DTLS-SRTP, ICE, OPUS) for browser-based calling.

- Work with mod_verto and SIP over secure WebSockets.

Reliability & Performance :

- Keep tabs on system health and call quality; dig through logs and CDRs.

- Tune codecs and RTP settings for better performance.

- Lead incident response and root-cause investigations for production issues.

Infrastructure :

- Run deployments on Linux (CentOS/Ubuntu) and cloud environments (AWS/GCP/Azure preferred).

- Build in high availability, load balancing, and scaling from the start.

- Team up with DevOps for CI/CD, backup strategy, and automation.

What You Bring :

- Real, hands-on FreeSWITCH experience - not just theoretical knowledge.

- Strong command of VoIP protocols (SIP, RTP, RTCP, WebRTC).

- Comfortable administering Linux systems.

- Able to write dialplans in XML, Lua, JS, or Python.

- Practical ESL experience for event-driven call control.

- Familiar with debugging tools like fs_cli, sngrep, and tcpdump.

- Working knowledge of SQL/MySQL/PostgreSQL for CDR data and reporting.

(ref:hirist.tech)