Abstract: A telephone isolation device having a latching relay operated switch in one of the telephone conductors which when the relay is actuated brings a voltage dividing branch circuit that includes a restoring coil of the relay into parallel with a subscriber's telephone. If the telephone is connected and off of the hook, the low impedance of the telephone keeps the flow of current to the restoring coil below an operable value. When the telephone is placed on the hook, all current thereafter passes through the restoring coil to again connect the telephone to the telephone conductors. The disconnect coil of the relay is actuated by applying a positive 100 volt DC current to both lines of the telephone system.