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A sync lockable subcarrier generator, dbx noise reduction encoding, audio processing, and peak deviation meter are all integrated into one box. A wideband noise source and AM detector are also provided for tuning the aural transmitter system for minimum synchronous AM.

The TSCA-189 fully conforms to the BTSC specifications for a SAP generator. The major necessary elements include:

1. A subcarrier whose average frequency can be locked to horizontal sync and remain locked regardless of the modulating signal.
2. A 50Hz to 10kHz audio bandwidth.
3. Noise reduction encoding employing the dbx noise reduction system that won the approval of the EIA's (now the CEA's) Multichannel Sound Committee.

For compatibility with various aural exciters and to allow easy integration with stereo TV audio the TSCA-189 provides two methods of connection to your aural exciter. In the first method, called "Loopthrough," the composite baseband signal is fed into the unit, buffered, and mixed with the SAP subcarrier. The combined output then drives the wideband input of the aural exciter. In the other mode, a separate high level SAP signal can feed the "SCA" or auxiliary input of many aural exciters as well as Modulation Sciences' STV-784WB Television Stereo Generator.

The audio processor portion of the TSCA-189 is explicitly designed for subcarrier modulation. It provides maximum intelligibility of dialogue and the best fidelity of music while delivering the greatest possible signal-to-noise ratio. Operation of the audio processor can be optimized for your needs by use of the separate broadband and high frequency limiter controls, as well as by setting the operating point of the compressor using the input level control.

• Subcarrier unconditionally locked to horizontal sync
• 50 Hz to 10kHz audio response
• dbx noise reduction for greater than 65 dB SNR
• Built in modulation monitor
• Integrated audio processor makes external processors unnecessary
• Sufficient input audio gain to allow direct connection to telephone lines
• Tuning aid minimizes aural transmitter synchronous AM
• Established hardware - basic design proven in FM SCA service
• Synthesized subcarrier generator can be programmed to other frequencies for TV SCA applications
• Excellent RF shielding
• Stable over a wide temperature range (0-50º C)
• Meets all requirements of EIA for SAP
• Crystal control takes over in the event of TV sync loss
• Muting circuit automatically switches off the subcarrier when audio is removed
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