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equipment that communicate using RS485 have introduced a small voltage bias to the
data lines. This is usually accomplished using a 470 Ohm resistance to +5V on the
positive line and 470 Ohm resistance to ground on the negative line. When used in
conjunction with the appropriate termination resistors referred to in the previous section,
this introduces about a 300 mV offset, improving noise immunity.
Offset bias for four wire RS485 can be applied on the MTX-8885 and MRX-8885 by
setting switch # 1 and switch # 3 down. Please note that these switches work as a set
and must be either both down or both up. In a majority of cases, bias will not be required
and these switches should remain in the up position. If using offset bias, it is important
that termination resistor switch # 2 and switch # 5 be in the down (applied) position.
Using offset bias without a termination on the line will cause communications to fail.
Offset bias for two wire RS485 can be applied on the MTX-8885 and MRX-8885 by
setting switch # 4 and switch # 6 down. Please note that these switches work as a set
and must be either both down or both up. In a majority of cases, bias will not be required
and these switches should remain in the up position. If using offset bias, it is important
that termination resistor switch # 5 be in the down (applied) position. Using offset bias
without a termination on the line will cause communications to fail.
LIFETIME WARRANTY INFORMATION
American Fibertek, Inc warrants that at the time of delivery the products delivered will be
free of defects in materials and workmanship. Defective products will be repaired or
replaced at the exclusive option of American Fibertek. A Return Material Authorization
(RMA) number is required to send the products back in case of return. All returns must
be shipped prepaid. This warranty is void if the products have been tampered with. This
warranty shall be construed in accordance with New Jersey law and the courts of New
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