40 in a step 546 if it is the blank timer is tested and is started in a step 544 if the bit counter is not equal to 40 control is transferred back to step 522 referring now to fig8 a through 8f and in particular to fig8 a the operation of the receiver is set forth therein in a step 700 an interrupt is detected and acted upon from the radio input pin the time difference between the last edge is determined and the radio inactive timer is cleared in step 702 a determination is made as to whether this is an active time or inactive time in a step 704 i e whether the signal is being sent with carrier or not if it is an inactive time indicating the absence of carrier control is transferred to a step 706 to store the inactive time in the memory and the routine is exited in a step 708 in the event that it is an active time the active time is stored in memory in a step 710 and the bit counter is tested in a step 712 if the bit counter zero control is transferred to a step.