Null modem adapter/ Gender changer

[big_d]

Can someone please explain the difference between a null modem adapter and a gender changer. Are they the same thing? The reason I ask is that I'm going to start using my laptop for logging and am going to buy the Keyspan serial to usb adapter. I have a gender changer that will work fine between my logging cable and the Keyspan unit, but I'm wondering if I need a "null modem adapter". Thanks, big_d

 

[snowborder714]

I would say you'd need a gender changer as it's use is to connect two cables together.

In serial communications, there exists a type of adapter that is similar in appearance to a gender changer, and in fact may provide the function of changing the gender, but is not the same thing. This device is called a null modem. Despite the word modem appearing in the name, it is not a modem. Rather, it is a device with the appearance of a gender changer that imitates the presence of a modem.

A normal gender changer simply changes the gender without rerouting any pins. Therefore, pin 1 connects to pin 1 on the other side, pin 2 connects to 2, pin 3 connects to 3, and so forth.

A null modem reroutes wiring so that two serial devices may connect directly to one another without any communications hardware (see RS-232). For example, a null modem crosses pins 2 and 3, so that pin 2 on one side is connected to pin 3 on the other. This causes the "transmit" from each side to be routed into the "receive" side of the other, similar to how a crossover cable is used in Ethernet to connect two devices directly without a hub or switch. Two to three other pairs are similarly crossed in a null modem.

A null modem may also act as a gender changer if it has the same gender connector on both sides. Other null modems have a different gender on each side. It is important to recognize that a null modem used in place of a gender changer (or a gender changer used in place of a null modem) will result in an inoperable connection, even if the connectors physically fit.

Taken from here:
Gender changer - Wikipedia, the free encyclopedia

 

[big_d]

Thank you, I'll have to give it a try. big_d