IBM System/36 - Page 48

Line Polarity
With both lines tied to the shield at the far end, measure (at the
nearest end):
• Conductor-to-conductor: Less than 110 ohms
4
• Each conductor to shield: Less than 70 ohms
4
A reading greater than 110 or 70 ohms, respectively, means there is
an open circuit.
After testing the line continuity and making any necessary
corrections, check the polarity as follows.
With conductor A of the cable plug tied to the shield at the far
end, measure (at the nearest end) from conductor A to the shield.
This should be less than 70 ohms; if it is over 70 ohms, lines are
crossed.
Widest Notch R9476037·2
The polarity of the line must be maintained for each cable segment
and for the entire cable run to ensure proper machine operation.
4 Values for shorter length are proportional because this is a linear function.
For example, a cable with half the maximum length would have half the
resistance.
Appendix A. Bulk Cable Information 41