Description:
The NTE789, a monolithic silicon integrated circuit, is a stereo multiplex decoder intended for FM multiplex systems.
This stereo multiplex decoder requires only one low–inductance tuning coil (requires only one adjustment for complete alignment), provides automatic stereo switching, energizes a stereo indicator lamp, and operates from a wide range of voltage supplies.
Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a low–distortion preamplifier and simultaneously applied to both signal, generated by a local voltage–controlled oscillator (VCO), is counted down by two frequency dividers to a 38kHz signal and to two 19–kHz pilot–tone supplied by the FM detector is compared to the locally generated 19–kHz signal in a synchronous detector.

FEATUREs:
• Requires the use of only one low–inductance tuning coil
• Automatic stereo switching
• Directly drives a stereo indicator lamp up to 100mA
• Includes driver for stereo–lamp indicator
• Operates from a wide range of power supplies: 10 to 16 volts
• Requires only one adjustment for alignment
• Switching from monaural to stereo and stereo to monaural produces no audible thumps
• Low distortion: under 0.5%
• Separate dc input permits stereo defeat or enable
• High signal output: directly drives audio amplifiers
• Excellent SCA (storecast) rejection: 55dB typ.
• High audio channel separation: 40dB typ.