The Blonder Tongue OC-12D is a professional-grade, passive RF (Radio Frequency) device designed to combine multiple television channel signals onto a single coaxial cable within a Master Antenna Television (MATV) or Cable Television (CATV) distribution system. As a passive output combiner, it requires no external power, operating purely through its internal, precision-tuned circuitry to merge signals from up to twelve different modulators or channel sources. This unit is essential in headend facilities for hotels, hospitals, apartment complexes, and educational campuses, where a custom lineup of broadcast and internally generated channels must be distributed clearly and efficiently to numerous television sets throughout the building. Its primary function is to consolidate these discrete RF signals into a unified, composite output ready for amplification and distribution across the property.

Constructed with high-quality components within a shielded metal enclosure, the OC-12D is engineered for minimal signal loss (insertion loss) and excellent channel-to-channel isolation. This isolation is critical to prevent adjacent channels from interfering with each other, which would manifest as visual "ghosting" or other impairments on the end-user's television. The device features carefully calibrated bandpass filters for each input port, ensuring that only the intended frequency for that specific channel is passed through to the common output. This precise filtering maintains the integrity and strength of each individual channel, preventing intermodulation distortion and preserving the overall quality of the entire channel lineup. The robust chassis is designed for standard 19-inch rack mounting, facilitating neat and organized installation in a headend rack alongside modulators, amplifiers, and other signal processing equipment.

Installation involves connecting the RF output of each individual channel source (like a satellite receiver, DVD modulator, or off-air demodulator) to a designated input port on the combiner. The single output port is then connected to the main distribution amplifier, which boosts the combined signal for transmission across the coaxial cable network. The OC-12D's reliability, passive operation, and precise RF performance make it a fundamental and trusted component for system integrators building robust and scalable in-house television distribution systems, ensuring viewers receive a stable, high-quality picture on every channel.