20
HIGH SPEED SHM-B ASYNC AND CARD
• If you don’t have errors, you should suspect
a problem with the twisted-pair cable.
SYMPTOM: Occasional data errors.
1. The transmission distance/data rate capability
may have been exceeded. Refer to
Chapter 1
for information about valid data transmission
distances and data rates.
2. There is a poor-quality loop (four-wire
circuit). Try using a different four-wire circuit,
or rewire the existing circuit.
3. Check the path of your four-wire circuit for
potential sources of interference (fluorescent
lighting, electrical motors, etc.). Such sources
of electrical noise can provide an environment
in which unwanted signals are induced onto
your four-wire circuit. Also, check to see if an
adjacent four-wire cable carrying a separate
data stream is creating crosstalk. It may be that
the data signal is jumping from the adjacent
cable onto the four-wire circuit between the
two High Speed SHM-B Async modems
(another type of induced signal).