answer is yes y a check is made in block 60 if the receiver is operating in the first part of wake up that is is bit b 3 0 if the answer is yes y the receiver reverts to being energised intermittently as indicated by block 62 in block 64 a check is made to see if the receiver is now operating in the second part of wake up that is b 3 1 if the answer is no n the flow chart reverts to the input of the block 62 but if it is yes y the flow chart proceeds to block 66 which relates to maintaining the energisation of the receiver of the consumer unit if the answer to the block 60 is no n indicating that the receiver is operating in the second part of wake up the flow chart proceeds also to the block 66 block 68 relates to the receiver receiving the start of message sequence som and the concatenated message mes block 70 represents the consumer unit responding to the message and reverting to a sleep mode the flow chart reverts to the block 50 for individual addressing of the consumer units the four bytes a 3 to a 0 of the address should have approximately random properties in order to maximise the chance that the consumer unit is able to reject the address being transmitted after receiving only one of the address bytes each byte may take one of 256 different values to facilitate.