3.0 CONFIGURATION
The Model 2702 features configuration capability via hardware switches . This section describes all possible hardware switch configu- rations of the Model 2702.
3.1 DIP SWITCH CONFIGURATION
The Model 2702 has eight internal DIP switches that allow configu- ration for a wide range of applications. The eight switches are accessed by opening the plastic case with a small screwdriver. Figure 1 (below) shows the location of the DIP switches on the bottom of the printed circuit board.
DIP Switches
ON
OFF
Figure 1. Model 2702 bottom view, showing location of DIP switches
The Model 2702 DIP switches (SW1, SW3 & SW4) can be config- ured as either “On” or “Off”. Figure 2 (below) shows the orientation of the DIP switches with respect to ON/OFF positions.
ON
OFF
Figure 2. Close up of DIP switches showing ON/OFF positions.
Default positions for Switches SW1, SW3, and SW4 are shown in the table on the following page. Descriptions of each switch follow the table.
SWITCH SET SUMMARY TABLE
Position | Function | Factory Default |
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SW1 | Line Coding | Off |
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SW3 | Clock Mode | Off |
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SW4 | Clock Mode | Off |
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NOTE: Switches SW2, SW5, SW6, SW7, and SW8 are not used.
Switch SW1: Line Coding
Use Switch SW1 to control the Network Line Coding options. Set these options to be the same as the Line Coding given to you by your Service Provider. If you are using two Model 2702s together as short range modems, set both units identically.
SW4 | Line Framing & Coding |
Off | HDB3 |
On | AMI |
Line Coding Options:
High Density Bipolar 3 (HDB3): In HDB3 coding, the transmitter deliberately inserts a bipolar violation when excessive zeros in the data stream are detected. The receiver recognizes these special violations and decodes them as zeros. This method enables the network to meet minimum pulse density requirements. Use HDB3 unless AMI is required in your application .
Alternate Mark Inversion (AMI): AMI coding does not inherently account for ones density. To meet this requirement, the user should ensure that the data inherently meets pulse density requirements.
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