Voice Software Developer

Essential Trading Systems Corp. is a manufacturer of specialized voice communication hardware and software. Since 1986, we have designed advanced VoIP, SIP, and Radio-over-IP (RoIP) solutions that enable instant, reliable communications for industries such as financial services, public safety, utilities, and dispatch operations. Our products integrate microphones, push-to-talk consoles, and gateway devices with modern IP networks to deliver clear, low-latency voice communication across multiple channels. By combining robust hardware design with innovative network technologies, we help organizations modernize legacy communication systems and deploy scalable, easy-to-manage solutions worldwide.Skills Required for Developer (Next Generation Linux-Based Device)Embedded Linux DevelopmentStrong experience developing software for embedded Linux systemsExperience with custom Linux distributions (Debian/Yocto/Buildroot)Kernel configuration, device drivers, and hardware interface supportBootloader and system startup (U-Boot or similar)Experience working with microSD or flash-based storage systemsLinux system optimization for embedded hardwareVoIP / SIP / NetworkingExperience implementing or maintaining SIP-based communications systemsKnowledge of RTP / RTCP media streamingFamiliarity with VoIP codecs such as G.711, G.729, Speex CS-74 Admin Setup Guide 09112025Understanding of NAT traversal, STUN, QoS (DSCP), and SIP registrationExperience integrating with PBX systems (Asterisk, FreeSWITCH, etc.)TCP/IP networking, DHCP, DNS, NTPAudio ProcessingExperience working with real-time audio streamingKnowledge of ALSA or similar Linux audio frameworksAudio mixing, buffering, and jitter controlExperience with microphone, speaker, and audio codec hardwareSignal processing basics (tone generation, filtering)Embedded Hardware IntegrationExperience interfacing with GPIO, audio codecs, microphones, and speakersKnowledge of Ethernet and PoE hardware integrationExperience integrating external peripherals such as:PTT buttonsFootswitchHandset/headset interfacesExperience working with low-level hardware debuggingWeb Interface DevelopmentExperience building embedded web configuration interfacesKnowledge of:HTTP/HTTPS servers on embedded devicesHTML / CSS / JavaScript UIBackend configuration interfaces (CGI, Python, C, or similar)Firmware Development & DeploymentExperience building firmware update mechanismsSecure update strategies and version managementExperience packaging firmware images for embedded devicesAbility to maintain backward compatibility where possibleSystem Diagnostics & LoggingExperience implementing Syslog, logging systems, and diagnostic toolsNetwork packet capture and debugging toolsTroubleshooting SIP and RTP trafficSecurityExperience implementing TLS / SRTP secure communicationsSecure authentication and credential handlingSecure firmware update processesDevelopment Tools & PracticesStrong experience with:C / C++ (primary for embedded Linux)Bash scriptingVersion control (Git)Cross-compilation toolchainsDebugging tools (GDB, Wireshark, tcpdump)Nice-to-Have (Bonus Skills)Experience with radio communication systems or dispatch consolesFamiliarity with DTMF signaling and tone controlExperience developing real-time systemsExperience with multicast audio streaming