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Loopback Plugs -

Loopback Plugs are used by testing software to test various functions of serial and parallel ports.

For each of the following examples the numbers next to the word "pins" show which pin numbers are connected to each other. For example "pins 1-7-8" means that pin 1 is connected to pin 7 and to pin 8, in effect pins 1, 7 and 8 are all connected to each other.

Serial 9-pin female

pins 1-7-8
pins 2-3
pins 6-4-9

Serial 25-pin female

pins 1-7
pins 2-3
pins 4-5-8
pins 6-11-20-22
pins 15-17-23
pins 18-25

Parallel 25-pin male

pins 1-13
pins 2-15
pins 10-16
pins 11-17
pins 12-14

Programs such Symantec's Norton Utilities, use these plugs to test the serial and parallel ports of a PC.

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