Connecting telephone hybrid d-sub pins to a switch?
Most telephone hybrid units intended for Broadcast use have an option for "Auto Answer", many also have the option for "Auto Disconnect".  

I haven't looked at the Studer Hybrids for decades and don't recall if they have that option.  

FWIW - my favorite Hybrids are something like the Getner DH20 or the version of the DH-20 customized for conferencing: AP-10.  That said: my last few projects have used Hybrids from Telos.