|There is no reason why you cannot connect a cable with RJ11 on one end and USB on the other. You just need the details of how the RJ11 end is wired and wire it to connect to the the USB standard which only needs four connections. The tech details for the device with the RJ11 should give you details.|
I have a device that connects with a cable that is USB on one end and RJ45 on the other. The reality is that is USB but only uses 4 of the eight available connections. They probably used an RG45 socket because if was cheaper than using a USB socket.