This device is designed to give the user the ability to connect to a dial tone even if there is another phone in use which maybe critical for emergency calls or prevent interruption of modem or fax transmissions. It can also assure line privacy.
There are two jacks - a priority and subordinate. The phone / fax connected to the priority jack takes priority over the phone / answering machine that are connected to the subordinate jack. When the subordinate line is in use an LED will light. If a user wants to use the phone/fax he must either wait until the LED is not lit or simply pick up the phone or dials the fax which cuts off the connection to the subordinate line. A dial tone will then be available to the priority phone or fax machine.
The phone/fax/modem connected to the priority line will not be interrupted if the subordinate user tries to connect. If the subordinate user attempts to use the phone while the priority devices is in use, there will be no dial tone or signal until the priority device is no longer in use.