I had this same problem a few years ago and went down the rabbit hole. I was looking for the US Robotics X2 and K56Flex handshake sounds and eventually found th

I had this same problem a few years ago and went down the rabbit hole. I was looking for the US Robotics X2 and K56Flex handshake sounds and eventually found them. V.90/92: https://goughlui.com/2016/05/03/project-the-definitive-collection-of-v-90v-92-modem-sounds/ https://goughlui.com/2016/05/03/project-the-definitive-colle... X2: https://goughlui.com/2018/06/10/project-record-a-us-robotics-x2-dial-up-modem-connection/ https://goughlui.com/2018/06/10/project-record-a-us-robotics... K56Flex: https://goughlui.com/2018/06/10/project-record-a-k56flex-dial-up-modem-connection/ https://goughlui.com/2018/06/10/project-record-a-k56flex-dia...