The Telos Zephyr XSTREAM is a professional-grade ISDN codec (coder-decoder) designed for high-quality, reliable audio transmission over digital telephone lines. It serves as a critical link for broadcasters, enabling remote interviews, live reports, and high-fidelity program exchange between studios and field locations worldwide. The codec compresses and encodes high-quality stereo or mono audio into a digital format suitable for transmission over ISDN (Integrated Services Digital Network) lines, which provide dedicated, high-quality digital connections. At the receiving end, another XSTREAM codec decodes the signal, reconstructing the audio with minimal latency and exceptional clarity. This technology was the industry standard for remote broadcasting for decades, prized for its reliability and consistent audio quality that far surpassed analog telephone lines.

The XSTREAM model incorporates advanced audio codecs, including MPEG AAC-LD and aptX, which offer near-transparent audio quality at various bitrates, allowing users to balance bandwidth use against fidelity. It features a comprehensive set of input and output connections for integrating with studio consoles, mixing desks, and telephone hybrids. A key feature is its sophisticated hybrid circuit and echo cancellation, which ensures clean two-way communication by preventing feedback even in complex talk-show setups. The unit also includes a built-in dialer, support for multiple ISDN line configurations (BRI or PRI), and often IP connectivity as a backup or alternative transport method, reflecting the transition from traditional ISDN to IP-based audio transmission.

Housed in a sturdy rack-mountable chassis, the Zephyr XSTREAM is built for 24/7 operation in demanding broadcast environments. Control is managed through a front-panel interface with a display and buttons, and often via PC software for remote configuration and monitoring. For broadcast engineers, this codec provides a dependable and high-performance solution for integrating remote talent into live programming. It ensures that audio from any location can be brought into the studio with the clarity and reliability required for professional broadcast, maintaining the seamless flow of live radio and television even when contributors are thousands of miles apart.