Why does my router disconnect when i get a phone call?

I recently purchased a new cable modem and netgear router. Before this i had a different cable modem and a different netgear router. With the old ones, the phone could ring and the internet would be fine. Now, whenever the phone rings, the connection dies. I dont think it is the wireless signal being interfered with because I lose get disconnected even if i do not answer the phone. We have a coax splitter that splits the cable like and then one goes to a modem for the phone and the other goes to the new modem for the internet, which is then connected to the router. Why i am having this issue?