I was really hoping to find an ISDN simulator with U-interfaces but anything I could find on eBay I wasn’t going to pay for since I had no documentation on how

I was really hoping to find an ISDN simulator with U-interfaces but anything I could find on eBay I wasn’t going to pay for since I had no documentation on how to configure/operate them. I’d try to make one myself if I wasn’t so good at killing hardware.