Any substitute / schematic for Mindstorms 2.0 IR tower?
There is no non-LEGO product that can substitute the infrared tower used for communicating with the RCX, as the USB and Serial towers use a very specific protocol that does not match that of other Infrared devices. Nonetheless, it does appear that there are schematics available for the IR Tower, courtesy of Mark Bellis:



I'm no expert on low-level electronics, but it looks like this site has a lot of additional information that could be useful if you want to replicate/manipulate the IR tower.