Your Wish:

"Interrupt a phone call for a priority alarm call"

TSS-2PI Two-Port Telephone Line Sharing with Outbound Priority

A two-port telephone sharing switch that can interrupt a call in progress and give the line to the priority device.

Flexie TelCo Switch Modem Router Switch

Programmable remote selection and control of three ports. Access via Touch-Tone. Optional remote AC power control and reset button reboots.