Abstract: An addressing arrangement is disclosed for systems in which communication is required between a main device and a plurality of associate devices. In the arrangement, access messages are used corresponding to states of shift register sequences. When the main device issues an access message, each associate device transforms the received access message to another access message which is applied to a subsequent associate device. The transformation of access messages allows the associate devices to be identical to each other and respond to the same predetermined access message since each device is uniquely identified by its location in the system. Each associate device also has the capability of being accessed by a prescribed access message which is not transformed by the associate device as it propagates through the system.