I have no trouble at all connecting my CEM40 to a PC when I follow these instructions: www.ioptron.com/v/ASCOM/iOptron_ASCOM_CEM40.pdf

I use the USB port on the mount, to make it work you need to install the FTDI driver on the PC: www.ftdichip.com/Drivers/VCP.htm

These instructions should also work for a CEM120 (if the USB port is used). I noticed the 'Install FTDI driver' part is not in the CEM120 instructions, so that may be the culprit.

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