This is not a RS232 USB dongle which has it's own issues with interfacing to older equipment (but same problem, no enough current to push or pull the signal). I have a 3v3/5v0 USB TTL dongle. It works with some equipment but it couldn't pull the signal to 5v0 interfacing to my HD6303 (Hitachi's 6803). I fixed this by using 2 gates on a 74LS04 with the USB dongles TX. Not sure how to solve this. Has anyone built such a set of line drivers? I'll be using a similar setup with a few other boards (EPROM burner, PT69-5, Microbox II, etc.). But those might be worse as I'll be using a ESP WiFi chip (3v3) as a terminal server. -- Linux Home Automation Neil Cherry kd2zrq@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies KD2ZRQ