.
APPENDIX B
S/T BUS CONFIGURATIONS
SHORT PASSIVE BUS
The short passive bus configuration allows the connection of up to eight TEs at any point on the bus. The bus length is limited to 600 feet, as illustrated in Figure B-1. To select this bus configuration, set switch 1-2 to the Short position. The bus ter- mination resistors (TRs) can be placed at any point along the bus. If the TEs have internal TRs that can be optioned, only one TE's TRs should be enabled. The TRs in the NT1 Type 400 are enabled by setting switches 1-3 and 1-4 to the ON posi- tion, and switches 1-5 and 1-6 to the OFF position. If the unterminated TEs are placed within 20 feet of the NT1, set switches 1-3 and 1-4 to the OFF position, and switches 1-5 and 1-6 to the ON position. The switch settings should always be maintained, unless an external 100 ¾ resistor is being used. If an external TR is used, set switches 1-3 through 1-6 to the OFF position.
*Is not needed if NT1Õs
TR
is used
Figure B-1: Short Passive Bus Configuration
EXTENDED PASSIVE BUS
This bus configuration allows the connection of up to eight TEs at ranges up to 3000 feet from the NT1 Type 400, as illustrated in Figure B-2.
To select this mode, set switch 1-2 to the Long position. A TR must be centrally located to the TEs. The TRs in the NT1 Type 400 are enabled by setting switches 1-3 and 1-4 to the ON position, and switches 1-5 and 1-6 to the OFF position. These switch settings should always be maintained, unless an external 100 ¾ re- sistor is being used. If an external TR is used, set switches 1-3 through 1-6 to the OFF position.
3000
FEET
160
FEET
*Is not needed if NT1Õs
TR
is used
Figure B-2: Extended Passive Bus Configuration
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