Interconnecting classic computers

Wireless ideas... Serial-to-Bluetooth modules exist, but they're about $50 the each for the bare module, which may be too pricey for a large configuration. Duplex-ness shouldn't be too much of an issue, given a sufficiently generous buffer. Diamond MMC had an interesting card back in the 90's that provided home networking by imposing an RF carrier on the telephone copper pair. I've still got a couple of these cards and they work pretty well. The box claims 10Mb/sec, but reality is more like 1Mb. Still faster than a modem, however. IR was pretty popular for a short time--you could even go around corners if you aimed the transceivers right. It sounds as if Tony just wants to go point-to-point, so there would be only a single transmitter on at any one time. Others have mentioned carrier-current setups, but unless they're pretty sophisticated, low-bandwidth and error-prone. I've got a copy of an article from an issue of the HP Journal back from the 80's, where a spread-spectrum carrier current system is described in detail. I wonder if one could simply buy a carton or two of old 900MHz cordless phones and jerry-rig something up? Come to think of it, I've never even tried interfacing a regular modem to a cordless phone handset. I wonder if it works... Cheers, Chuck