American FiberTek Inc. RT-89TX Intercom Rack Card

The AFI RT-89TX Rack Card Transmitter Interface from American Fibertek delivers a clean, bi-directional intercom link on a single multimode fiber for TOA systems, mounting as a rack card in AFI card cages such as SR-20/2 or SR-20R/1. It transmits one channel of bi-directional audio plus a contact-closure signal, supports VOX transmission, and FM-modulated audio, with diagnostic indicators for Power and Optical Presence to quickly verify system status. The unit uses multimode fiber at 850/1300 nm and employs an ST fiber connector, aligning with TOA intercom networks (e.g., VS900 to RS150/160/170) for cross-system compatibility. Key specifications include an audio bandwidth of approximately 300 Hz to 10 kHz, THD around 2% at 1 kHz, and an SNR near 50 dB, reflecting low-distortion voice transmission over the fiber link. This rack-card transmitter is designed for stand-alone operation or as part of AFI’s modular intercom architecture, ensuring a transparent signal path where input microphone and audio levels can be balanced at the source for reliable, two-way communication across campus or facility intercom networks.