The IR interface on the RCX is able to communicate with Spybots, Scout Bricks, Lego Trains, and the NXT (using a third-party infrared link sensor). The RCX 1.0 IR receiver carrier frequency is 38.5 kHz, while the RCX 2.0 IR carrier frequency is 76 kHz. Both versions can transmit on either frequency. The RCX communicates with a computer using a Serial or USB IR tower. As the RCX is discontinued, support for the interface is limited on more recent operating systems than Windows XP.