PassMark Software

Serial and Parallel Loopback Plugs

High Quality, Fully-Molded Serial and Parallel Loopback Plugs

Loopback plugs are the quickest, most effective way to test that a PC's serial (RS232) and parallel ports are working correctly. These adapters plug into the serial and parallel ports of a computer, allowing the looping of the data and signal path by joining the transmit and receive pins together. These loopback plugs are designed to work in conjunction with BurnInTest Professional allowing the quick diagnostic and troubleshooting of problems affecting serial and parallel ports.

The Serial Loopback Plug is a 9 pin female plug (DE-9) and the Parallel Loopback Plug is a 25 pin male plug (DB-25).

In addition to testing the receive and transmit functions, the following RS232 signal pins are also tested by the Serial Loopback plug: Clear To Send (CTS); Request To Send (RTS); Data Set Ready (DSR); and Data Terminal Ready (DTR).

Serial loopback plugs

Quantity Price (USD) Ordering
1 - 4 $9.50 Add to cart
5 - 10 $8.55
11 or more $7.60

Parallel loopback plugs

Quantity Price (USD) Ordering
1 - 4 $12.00 Add to cart
5 - 10 $10.80
11 or more $9.60

These prices do not include shipping and do not include the BurnInTest Professional software.


No cabling is required as these plugs are designed to connect directly to the back of a PC. If a cable is used, then it should be a straight through cable.


Window 98, ME, 2000, 2003, XP (32-bit and 64-bit), Vista (32-bit and 64-bit), 2008 Server (32-bit and 64-bit), Windows 7 (32-bit and 64-bit), Windows 8 (32-bit and 64-bit), Windows 10 (64-bit) and Linux platforms are supported, provided you have the correct version of BurnInTest.

In order to use the plugs with Windows, BurnInTest Professional v2.0 or above is required. For Linux, BurnInTest for Linux v1.0 or above is required.

As there are several ways to build loopback plugs, we can not guarantee the compatibility of our plugs with any software except BurnInTest Professional.

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Serial Loopback Product Code: PM012
Parallel Loopback Product Code: PM013

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