Review on StarTech.com DB9 RS232 Serial Null Modem Adapter - F/F - NM9FF - High-performance, Reliable Data Transfer by Jon Larjin

This is a buggy implementation of a null modem and will not work in many applications. DTR on one side needs to be connected to DCD and DSR on the other side. However, this non-zero modem only connects the DTR to the DSR and connects the two DCD signals together, which is totally useless as no DTE needs to control the DCD, and non-functional as no DTE ever sees the DCD set becomes. In addition, two RI signals are connected to each other. Correctly they should only be disabled at both ends, but at least this second issue will not cause problems as no DTE should be driving the RI. Don't send it back as shipping will cost more than the price.