I'm trying to find a cable that can SEND a TTL signal from a computer running DirectRT to an external data acquisition system that take a voltage input (up to 10 mV) with a BNC connection (we do not need to receive any information in DirectRT - we're just marking when stimuli are presented to sync up behavioral and physiological responses). I can go out of my computer via either USB or a 9-pin serial connection, but this overall connection seems to be pretty odd because I haven't found anybody who stocks anything like it. Does anybody know of any retailers who have this type of cable? Any and all advice/comments would be appreciated. Thanks!

-David