Motorola 326X V.34 User Manual page 177

For example, assume you require a 30-foot cable. You intend to operate your
modem at 64.0 kbps. After looking at Table B-4, you determine that the
maximum capacitance for the cable is 900 pF. According to the formula above,
divide 900 pF by 30 feet. The result is 30 pF per foot:
900 pF
= 30 pF/ft
30 ft
Motorola recommends you use Motorola cables to attach your 326X modem(s) to
DTE(s). Use Table B-5 to select cable(s) for your application.
To use non-Motorola cables, Table B-6 provides examples of vendor cable wire
length versus DTE rates for 326X stand-alone units. NOTE: The part numbers
specified in Table B-6 are not for complete cables, but for the wires that are available
with the correct capacitance to support the higher rates of the 326X Modem.
Table B-5.
Motorola DB-25 Low Capacitance Cables for 326X
Motorola
Product
Description Code
Motorola 92153
Male 25-Male 25
92152
Straight-through
92151
92150
Motorola 92157
Male 25-Female 25
92156
Straight-Through
92155
92154
Motorola 92161
Male 25-Female 25
92160
Crossover
92159
92158
NOTE: Motorola DB-25 Cables have a conductor capacitance of 11 pF/ft and a shield
capacitance of 20 pF/ft for a total capacitance of 31 pF/ft. For example, operating at 19.2
kbps, a 50-ft length of cable multiplied by a total capacitance of 31 pF/ft yields a maximum
allowable cable capacitance of 1550 pF, which is acceptable in accordance with Table B-4.
Up to 19.2 Up to 64.0
kbps (ft) kpbs (ft)
50 30
50 30
50 30
Cabling and Interface Pinouts B-9
Up to 96.0 Up to 115.2
kbps (ft) kbps (ft)
10 6
10 6
10 6