Aiphone - AT-406 andset-to-Handset System, White (AT-206, AT-306)Box set with AT 206 white audio master station and AT 306 white audio sub master station. Features Set includes 1 AT 206 master station and 1 AT 306 sub master station Master station calls all connected sub stations Sub stations call the master station only Powered by 6V DC or 4 AA batteries Up to two additional sub stations can be added (AT 306) Specs Communication Handset (full duplex) Wire Type Master Station to Sub Station: 2 cond., overall shield