CMX631AD5 CML Microcircuits, CMX631AD5 Datasheet - Page 7

• Manufacturer Part Number: CMX631AD5
• Description: Low Voltage SPM Detector
• Manufacturer: CML Microcircuits

Low Voltage SPM Detector
4.3 Sensitivity Setting
The CMX631A input sensitivity can be accurately adjusted and set to support many national 12kHz and 16kHz
SPM specifications.
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
2. Mark the intersection of the upper horizontal line and the upper sloping line; drop a vertical line from this
3. Mark the intersection of the lower horizontal line and the lower sloping line; drop a vertical line from this
4.3.1
1998 Consumer Microcircuits Limited
represents the required ‘Must’ decode level. The lower line represents the required ‘Must-Not’ decode level
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.
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.
Input Gain Calculation
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CMX631A
D/631A/1