TVS 3003 Limiter and Generator
The TVS-3003 is a combination MTS generator and audio limiter which combines advanced AGC and limiting audio processing with a state-of-the-art digitally synthesized MTS generator. It provides a single package stand-alone stereo television audio system.
Through the use of time tested circuit technology and innovative packaging, the TVS-3003 lets you to convert to stereo both quickly and easily. In addition, it includes a long list of "must have" features that will make your station's audio quality stand out.
- L/R or L + R/L − R Audio Input
- 20dB Input AGC Range
- Program Controlled Stereo Enhancement
- Variable Transfer Function Pre-emphasis Limiting
- Sync Input/Video Sync Separator
- Digitally Synthesized Stereo Generation
- Advanced 15.734 kHz Input Filtering
- CRL Improved dbx® Noise Reduction
- Full Function Diagnostic Metering
- On-Board Bessel Tone Calibration Generator
The TVS-3003 input circuitry consists of a wideband AGC circuit with over 20 db of range control that satisfies most all on-air AGC needs without additional level control.
When used with our deluxe TVS-3001 studio processing unit, this AGC is used lightly as a level safety net between the two units or any microwave link which may be connecting them.
True Stereophonic Enchancement
The received stereo effect perceived by your viewers is usually poor and is caused by their television's speaker spacing being too close together.
The TVS-3003 provides a method to overcome this and allows you to 'stand out' from your competition. We have provided an exclusive stereo image enhancer which dramatically improves your station's received stereo effect on both small and large television sets. By using our special enhancement system, you can automatically increase program separation within a defined range to cause dramatic stereo separation improvements.
YOU decide how much maximum enhancement should be allowed by the automatic circuitry and the system takes care of the rest. Further control is provided by allowing enhancement to begin only after a user defined minimum separation level has been acheived. (Selectable at 6db or 12db) Mono sources remain unaffected.
Variable Transfer Function Limiting
To preserve the transmitted stereo audio fidelity, we designed a new limiting system especially for pre-emhasized MTS broadcasts. This system is free from the distortions which are caused by most other methods.
This system modifies the transmitted pre-emphasis curve through independent attenuation of the 1 kHz to 6 kHz and 6 kHz to 15 kHz segments of the audio spectrum. This allows full modulation of both segments of frequencies even if one band needs to be severely limited to prevent its over-modulation.
Today's dynamic audio programs often contain material with high peak to average ratios and peaks of short duration. The most common approach used to control these peaks is to employ simple clipping circuits. The high frequency distortions found on many television stations today are caused by these kind of limiters. Our TVS-3003 final peak limiting design is free of such side effects.
We provide a unique instantaneous peak limiting system which actively monitors average peak levels and adjusts both average levels and instantaneous peak levels depending on the amount peak level content. The result is 100% peak control and no side effect distortions.
Advanced Audio Low-Pass Filtering
Our MTS generator uses a distributed 14th order filtering system rather than the standard BTSC 11th order topology.
Our low pass filtering consists first of one pair of 7th order filters in left and right channels and another pair of 7th order filters in the L+R/L-R generator paths.
This method maintains superior stereo separation specifications, excellent pilot and subcarrier protection that cannot be obtained with an 'ALL-IN-ONE' 11th order filtering system. It also produces less group delay in each filter section which is important in L-R since the filter is in the dbx compressor loop.
dbx Encoding With CRL L-R Noise Reduction
We at CRL have found that during quiet passages, the pre-emphasis gain of dbx encoders increases by about 60 db! This is the ,strong>NORMAL characteristic of dbx encoders and results in their L-R noise floor rising substantially.
We also determined that some television receivers could detect this noise and therefore developed a unique gating technique which prevents the excessive dbx gain from taking place when L-R approaches low levels (no separation).
The result of this intelligent gating action is up to a 20 db lower L-R noise floor than ALL other MTS generators currently on the market.
Digital Stereo Generation
Our MTS stereo L-R subchannel modulator is a CRL pioneered and time proven digitally synthesized design. Its circuitry provides totally transparent and drift free L-R subchannel generation.
Featuring a unique PAM (pulse amplitude modulator), our design takes advantage of being a digital switching modulator while acting as an apparent 'ANALOG' balanced modulator. This produces the high stability and precision found in digital modulators and provides the high linearity found in balanced modulators.
Ultimately, our modulator provides both a drift free and spectrum pure design which resists aging effects that occur with other designs.
Sync/Video Lock Input
The TVS-3003 will accept a WIDE range of sync or video signals so that the generator will lock to Fh as required by the FCC. The input impedance is high and has a rear panel loop through connection if desired.
Our unit is normally set up to return to mono operation upon loss of sync lock and will indicate a sync failure/loss of lock condition on its front panel as well as any remote status indicators.
Versitle Outputs
The CRL TVS-3003 features two independent low impedance outputs with selectable output impedances of 10 or 75 ohms. The lower impedance positions allow for driving long lengths of transmission lines without additional outboard drivers.
We provide the second, or auxiliary, output as selectable for either an unbalanced or balanced composite or as a monophonic audio output. This selection is front panel controlled.
Either output level is independently controlled from behind the security door on the front panel.
Metering and Controls
The TVS-3003 quick and easy setup is enhanced by the inclusion of a metering system that allows selection of virtually all vital operating parameters on a LED display panel.
Metering functions and input ranges are selected either by a front panel push button or by configuration switches mounted behind the front panel access door.
Mutli-color status indicators continuously monitor generator status. All normally used level and control functions are mounted behind the front panel access door. Many additional options are available on internal circuit board jumpers.
Our internal Bessel tone calibration signal allows easy level alignment of proper ON AIR modulation levels.