CMX631A データシートの表示（PDF） - CML Microcircuits

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CMX631A

Low Voltage SPM Detector

CML Microcircuits 

Low Voltage SPM Detector

CMX631A

4.3 Sensitivity Setting

The CMX631A input sensitivity can be accurately adjusted and set to support many national 12kHz and 16kHz

SPM specifications.

4.3.1 Input Gain Calculation

The input amplifier, with external circuitry, is used to set the sensitivity of the CMX631A to conform to the user's

national level specification with regard to ‘Must’ and ‘Must-Not’ decode signal levels.

With reference to the graphs in Figure 4 and Figure 5, the following steps will assist in the determination of the

required gain/attenuation.

1. Draw two horizontal lines from the Y-axis [Signal Level (dB)] in Figure 4 and Figure 5. The upper line

represents the required ‘Must’ decode level. The lower line represents the required ‘Must-Not’ decode level

2. Mark the intersection of the upper horizontal line and the upper sloping line; drop a vertical line from this

point to the X-axis [Amplifier Gain (dB)]. The point where the vertical line meets the X-axis indicates the

minimum Input Amp gain required for reliable decoding of valid signals.

3. Mark the intersection of the lower horizontal line and the lower sloping line; drop a vertical line from this

point to the X-axis. The point where the vertical line meets the X-axis will indicate the maximum allowable

Input Amp gain. Input signals at or below the ‘Must-Not’ decode level will not be detected as long as the

amplifier gain is no higher than this level.

© 1998 Consumer Microcircuits Limited

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D/631A/1

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