These Substations have a call button, which is used to call the Master station. A tone on the Master will sound and an LED above the corresponding substation button will light. Once the Master responds by pressing the Talk button, the Substation can then talk hands free and the Master station operator will need to press the Talk button to reply.
Substations cannot communicate with each other.
Only two conductor wiring is needed from a Substation to the Master. Substations cannot share a wire with each other.